law of inertia experiment

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Easy Inertia Experiment

May 29, 2020 By Emma Vanstone Leave a Comment

This inertia experiment is super easy and a great fun science trick for kids and adults!

If you want to learn more about Isaac Newton’s Laws of Motion or forces in general I’ve got lots more forces and motion experiments you can try!

What is inertia?

Isaac Newton’s First Law states that an object stays still or keeps moving at the same speed and in a straight line unless it is acted upon by a force.

In simple terms that means if an object isn’t moving ( imagine a book on the floor ) it won’t start to move unless a force makes it move ( for example, if you push the book ).

Isaac Newton’s First Law is known as the Law of Inertia .

You’ll need:

Card folded into a triangle column and taped securely.

Piece of card – A5 size

Small object that is big enough to sit on top of the column.

Inertia Experiment Instructions

Place the A5 sheet of card on top of the pint glass.

Carefully put the triangular column on the card.

Balance the lemon on top of the column, it needs to be directly above the glass.

Hold the glass with one hand and then quickly pull the A5 card with the other hand.

The lemon should drop into the glass!

Why does this work?

The lemon is heavier than the cardboard column which means it doesn’t move as easily as the column when the cardboard is pulled from underneath.

There isn’t a sideways force acting on the lemon so it falls straight down because of gravity.

Newton’s First Law states that an object at rest remains at rest unless acted on by a force.

More Forces Experiments for Kids

Design, build and launch a water powered bottle rocket !

Learn about potential energy with a cotton reel car or make a balloon powered car .

Learn more about Newton’s Laws of Motion and how they apply to space travel in my book, This IS Rocket Science!

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Last Updated on May 29, 2020 by Emma Vanstone

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Simple Science Experiments: Newton’s First Law of Motion

by Steve Davala

Many years ago, Sir Isaac Newton came up with some most excellent descriptions about motion. His First Law of Motion is as follows: “An object at rest stays at rest and an object in motion stays in motion unless acted upon by an outside force.” Quite a mouthful. What that means is that something that is sitting there will continue to sit there unless moved. And something moving will keep moving unless something stops it.

Still a mouthful. Just think about this: When you are at a stoplight in your car and you start moving quickly, you feel pushed back into your chair. The opposite is true if you come to a sudden stop, and you move keep moving forward, with only your seatbelt preventing you from crashing forward.

Here are a couple of experiments that demonstrate this very cool law of motion; in a word called “inertia.”

Ball Bounce Experiment

Materials for the Ball Bounce Experiment:

• A basketball or soccer ball, or similar bouncy ball
• a smaller bouncy ball (like a tennis ball or a racquet ball).
• Have an assortment of other balls handy for further experimenting.
• Do this experiment outside
• First bounce the basketball and tennis ball side by side to compare their bounces. Start them off around chest height
• Make a hypothesis (a guess) about what will happen when you stack the small ball on top of the bigger one and then drop it
• Try it! It may take a couple tries to line them up just right but the results are pretty awesome

Explanation:

The energy of motion from the bigger ball is transferred into the smaller one. Most of your attention is on the sky-rocketing smaller ball, but if you look at the basketball, it doesn’t have much bounce at all!

Experiment further:

Hopefully this will make you think of other things. Like what if you switched the two balls and dropped the smaller one on the bottom? What if you used two of the same sized ball? A golf ball on top? Think of other things!

Penny on a Card Experiment

Materials for the Penny on the Card Experiment:

• a small plastic cup,
• a playing card

Procedure :

• Put a playing card on top of the plastic cup
• Put a coin on top of the card
• With a sharp flick, hit the card out from under the coin! Or pull it really quickly toward you.
• The coin will drop into the cup.

The coin has inertia, meaning it really wants to stay in one place. If you move the card slowly, it isn’t fast enough to overcome that force. If you flick it quickly, the coin stays in one place and then drops into the cup. An object at rest will remain at rest. If you are brave, put the card on your finger and the coin on top… try to flick the card out until the coin stays on your finger. It can be done!

Use a sheet of printer paper with a few heavier (non-breakable) objects on it. See if you can quickly pull the paper out from under the objects.

Another cool example of inertia: Put your hand, palm side up, next to your ear. Put a coin on your elbow. In one swift motion, bring your hand straight forward and try to catch the coin before it drops. If you’re fast (and lucky) enough, you will catch the coin before gravity has a chance to bring it down.

I hope you enjoyed this simple experiment and learned a little bit about the first law of motion and inertia. If you have more questions about this, or need tips about science fair ideas around this topic (or others), feel free to contact me.

Steve Davala is a middle school science teacher who likes to write. He’s got two kids of his own and subjects them to these science activities as guinea pigs. Follow him on Twitter or email him at [email protected] .

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Course: physics archive   >   unit 3.

• Newton's first law of motion introduction
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Why do objects slow down?

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4.2 Newton’s First Law of Motion: Inertia

Learning objectives.

By the end of this section, you will be able to:

• Define mass and inertia.
• Understand Newton's first law of motion.

Experience suggests that an object at rest will remain at rest if left alone, and that an object in motion tends to slow down and stop unless some effort is made to keep it moving. What Newton’s first law of motion states, however, is the following:

Newton’s First Law of Motion

A body at rest remains at rest, or, if in motion, remains in motion at a constant velocity unless acted on by a net external force.

Note the repeated use of the verb “remains.” We can think of this law as preserving the status quo of motion.

Rather than contradicting our experience, Newton’s first law of motion states that there must be a cause (which is a net external force) for there to be any change in velocity (either a change in magnitude or direction) . We will define net external force in the next section. An object sliding across a table or floor slows down due to the net force of friction acting on the object. If friction disappeared, would the object still slow down?

The idea of cause and effect is crucial in accurately describing what happens in various situations. For example, consider what happens to an object sliding along a rough horizontal surface. The object quickly grinds to a halt. If we spray the surface with talcum powder to make the surface smoother, the object slides farther. If we make the surface even smoother by rubbing lubricating oil on it, the object slides farther yet. Extrapolating to a frictionless surface, we can imagine the object sliding in a straight line indefinitely. Friction is thus the cause of the slowing (consistent with Newton’s first law). The object would not slow down at all if friction were completely eliminated. Consider an air hockey table. When the air is turned off, the puck slides only a short distance before friction slows it to a stop. However, when the air is turned on, it creates a nearly frictionless surface, and the puck glides long distances without slowing down. Additionally, if we know enough about the friction, we can accurately predict how quickly the object will slow down. Friction is an external force.

Newton’s first law is completely general and can be applied to anything from an object sliding on a table to a satellite in orbit to blood pumped from the heart. Experiments have thoroughly verified that any change in velocity (speed or direction) must be caused by an external force. The idea of generally applicable or universal laws is important not only here—it is a basic feature of all laws of physics. Identifying these laws is like recognizing patterns in nature from which further patterns can be discovered. The genius of Galileo, who first developed the idea for the first law, and Newton, who clarified it, was to ask the fundamental question, “What is the cause?” Thinking in terms of cause and effect is a worldview fundamentally different from the typical ancient Greek approach when questions such as “Why does a tiger have stripes?” would have been answered in Aristotelian fashion, “That is the nature of the beast.” True perhaps, but not a useful insight.

The property of a body to remain at rest or to remain in motion with constant velocity is called inertia . Newton’s first law is often called the law of inertia . As we know from experience, some objects have more inertia than others. It is obviously more difficult to change the motion of a large boulder than that of a basketball, for example. The inertia of an object is measured by its mass . Roughly speaking, mass is a measure of the amount of “stuff” (or matter) in something. The quantity or amount of matter in an object is determined by the numbers of atoms and molecules of various types it contains. Unlike weight, mass does not vary with location. The mass of an object is the same on Earth, in orbit, or on the surface of the Moon. In practice, it is very difficult to count and identify all of the atoms and molecules in an object, so masses are not often determined in this manner. Operationally, the masses of objects are determined by comparison with the standard kilogram.

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They are equal. A kilogram of one substance is equal in mass to a kilogram of another substance. The quantities that might differ between them are volume and density.

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Home » Articles » STEM » STEM Science » What is Inertia and how to demonstrate it

What is Inertia and how to demonstrate it

Change is hard, we all know it. and we don’t mean that in a purely psychological sense. did you know that is one of the fundamental laws of the universe resistance to change even has a name – inertia, and it’s a very important topic in physics. let’s explore all about it in this super simple, but effective experiment., article contents.

What is inertia exactly?

People used to think that objects have a natural tendency to stop. If you want them to continue moving, you have to apply some kind of force again. And that is something that we can observe in everyday life as well. If we throw a ball, it won’t just keep on moving forever. It will fall down on the ground. Everything will stop eventually.

But that notion was challenged in the 1600s by Galileo , and later, Newton and Descartes . Galileo was studying planetal orbits and noticed something strange. Objects will actually continue to move unless some force causes them to stop. This discovery helped to explain how is it possible that we don’t feel any motion even though Earth revolves around the Sun. We are moving together with Earth so from our perspective, it looks like it stands still.

Sometimes we can observe a similar effect on a smooth ride. If we don’t see or hear anything, it would be hard to say if we are actually moving or standing. That new insight was called the Law of Inertia .

Inertia is defined as the object’s tendency to continue doing what it was doing – if it was moving to continue to move and if it was resting to continue resting. This second part does align with our everyday life – objects don’t start moving by themselves. But we all know objects eventually stop. So how can this be true?

But here comes the caveat – they will continue what they were doing unless acted upon by some net force . The net force is just the sum of all the forces that act on an object. Our environment interacts with us in various ways and there are a lot of acting forces. Friction and gravity being the most obvious.

When we roll a ball it will come to a stop because of the friction . If there was no friction it would continue to move (unless acted upon by some other unbalanced force). We can notice that by comparing surfaces with different levels of friction. For example, ground and grass produce much more friction when the ball rolls, so the ball will stop sooner. Ice, on the other hand, would cause the ball to roll much, much longer. If there was no friction at all, like in a vacuum , the ball would never stop. And that’s actually true in the space!

All objects resist change, but the bigger they are (the more mass they have), the harder it is to change. We know that intuitively. We know that it’s harder to move (and stop!) a huge boulder than a tennis ball.

What is motion and properties that describe a movement

Motion is one of the key topics in physics. And no wonder, since it’s fair to say that everything in our universe is constantly in motion. Science of motion answers so many important questions. Like where you are, where you have been and where are you going.

Motion can be one-dimensional, for example, a car going in a straight line. Or it can be multidimensional – like submarine who can also move up and down.

We can define motion as a change in the position of some object in a certain amount of time . Besides distance and time, there are some other properties that describe motion.

When talking about a change in position, there are two important terms: distance and displacement .

Distance is a scalar quantity. It tells us the total amount of travel from the start position to the end position. All changes in position are added together, no matter the direction. If we walk 50m west and then 20m back east, our total distance will be 70m.

Displacement is a vector quantity. It takes into consideration direction, so in the same example, our total displacement will be 30m west. If the object travels in a straight line in just one direction, distance and displacement will be of the same amount. We should always preserve direction when talking about displacement though!

A similar case is with speed (scalar) and velocity (vector). Speed tells us how fast the object is moving, and its formula is the distance over time. Velocity is similar to speed, but with direction.

Unlike speed which is interested in the total distance you traveled in a certain time, velocity cares for displacement (change in position). If there is no displacement, for example, you move left 10 steps and then right 10 steps, you still moved with some non-zero speed. However, your velocity will be zero.

The last important term is acceleration . Acceleration is the change in velocity and we perceive it as speeding up or slowing down. Since velocity also includes direction, even change in direction is considered acceleration. What’s tricky about acceleration is that we often confuse it with velocity or speed. If something is moving very fast, it has to have a high acceleration, right? No, actually. The only thing that matters is if there is a change in velocity (speed or direction).

Principles of Newton’s laws of motion

Philosophiae Naturalis Principia Mathematica was published in 1687. It’s Isaac Newton’s life work and one of the most influential books in the history of mankind. It proposed fundamental laws of motion that are still in use today. Usually called Newton’s Laws of Motion , they changed the way we perceive the world and are the foundation of classical mechanics (sometimes even called Newtonian Physics ).

There are 3 of them , usually called just First, Second and Third Newton’s law. Good news, you already know everything about the First law . Newton took Galileo’s Law of inertia and rephrased it. To be fair, he did give credit to Galileo. It states that “A body at rest will remain at rest, and a body in motion will remain in motion unless it is acted upon by an external force.”

The Second Law of Motion describes what happens to an object when it is acted upon by an external force. It’s defined as “The force acting on an object is equal to the mass of that object times its acceleration.” You probably know famous formula F = m * a , which describes this law. Even the First law can be derived from this formula, it’s the special case when acceleration is 0. No change in velocity means there was no force.

The Third Law of Motion states, “For every action, there is an equal and opposite reaction.” It’s also descriptively known as Law of action and reaction. When there is an interaction between bodies, they apply symmetrical forces to each other. Same in magnitude, but opposite in direction. A good example is launching the spacecraft and you can even test it out for yourself by building a homemade rocket using vinegar and baking soda, or by making a rocket using the matches .

Materials needed for demonstrating inertia

• Bigger empty cup, ideally transparent
• Chain of beads (we used simple beaded Christmas garland)

Instructions for demonstrating inertia

We have a video on how to demonstrate inertia at the start of the article or continue reading instructions below if you prefer step by step text guide.

• Put the chain of beads in the cup slowly so it doesn’t get entangled.
• Raise the cup from the ground and pull slightly on the chain’s end.
• Enjoy the show! 🙂

Explanation of the Inertia Experiment – Why does it jump upwards?

What is this sorcery? How are beads defying gravity?

The phenomenon of “ chain fountain ” caught the public’s attention when it was showcased in a YouTube video by Stephen Mould in 2013. It caused lots of attention and research in the physics community. The key is in the structure of the chain and the fact that beads are connected to each other.

When pulled upward, links connecting the beads rotate , and beads bump into each other. This produces a huge downward force on the opposite end of the chain. That, as we know from Third Newton’s law means that the opposite force of equal magnitude is created. So our seemingly small pull generates huge push from the other side of the chain which causes beads to go upward.

What will you develop and learn

• What is inertia
• Properties of motion
• Newton’s laws of motion
• That science is fun! 🙂

If you liked this activity and are interested in more physics experiments, we recommend exploring heat conduction or try crushing can with air pressure . Sounds cool? It really is. If you want to just sit and think in peace, we have you covered. Hanoi tower is an ancient puzzle that will surely challenge your logical thinking (and patience!). Learn how to make your own Hanoi tower and even how to solve it .

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Newton's First Law

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Newton's first law of motion is often stated as

An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force .

Two Clauses and a Condition

There are two clauses or parts to this statement - one that predicts the behavior of stationary objects and the other that predicts the behavior of moving objects. The two parts are summarized in the following diagram.

There is an important condition that must be met in order for the first law to be applicable to any given motion. The condition is described by the phrase "... unless acted upon by an unbalanced force." As the long as the forces are not unbalanced - that is, as long as the forces are balanced - the first law of motion applies. This concept of a balanced versus and unbalanced force will be discussed in more detail later in Lesson 1 .

 Suppose that you filled a baking dish to the rim with water and walked around an oval track making an attempt to complete a lap in the least amount of time. The water would have a tendency to spill from the container during specific locations on the track. In general the water spilled when:

• the container was at rest and you attempted to move it
• the container was in motion and you attempted to stop it
• the container was moving in one direction and you attempted to change its direction.

Everyday Applications of Newton's First Law

There are many applications of Newton's first law of motion. Consider some of your experiences in an automobile. Have you ever observed the behavior of coffee in a coffee cup filled to the rim while starting a car from rest or while bringing a car to rest from a state of motion? Coffee "keeps on doing what it is doing." When you accelerate a car from rest, the road provides an unbalanced force on the spinning wheels to push the car forward; yet the coffee (that was at rest) wants to stay at rest. While the car accelerates forward, the coffee remains in the same position; subsequently, the car accelerates out from under the coffee and the coffee spills in your lap. On the other hand, when braking from a state of motion the coffee continues forward with the same speed and in the same direction , ultimately hitting the windshield or the dash. Coffee in motion stays in motion.

There are many more applications of Newton's first law of motion. Several applications are listed below. Perhaps you could think about the law of inertia and provide explanations for each application.

• Blood rushes from your head to your feet while quickly stopping when riding on a descending elevator.
• The head of a hammer can be tightened onto the wooden handle by banging the bottom of the handle against a hard surface.
• A brick is painlessly broken over the hand of a physics teacher by slamming it with a hammer. (CAUTION: do not attempt this at home!)
• To dislodge ketchup from the bottom of a ketchup bottle, it is often turned upside down and thrusted downward at high speeds and then abruptly halted.
• Headrests are placed in cars to prevent whiplash injuries during rear-end collisions.
• While riding a skateboard (or wagon or bicycle), you fly forward off the board when hitting a curb or rock or other object that abruptly halts the motion of the skateboard.

• Meaning of Force

Home Experiment: Newton's First Law/Law of Inertia

Introduction: Home Experiment: Newton's First Law/Law of Inertia

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law of inertia

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• Live Science - Inertia & Newton's First Law of Motion
• Academia - The Law of Inertia: How Understanding its History can Improve Physics Teaching
• The Physics Classroom - Newton's First Law
• Khan Academy - What is Newton's first law?
• OpenStax - Physics - Newton's First Law of Motion: Inertia
• Physics LibreTexts - The Law of Inertia
• BCcampus Open Publishing - Newton’s First Law of Motion: Inertia

law of inertia , postulate in physics that, if a body is at rest or moving at a constant speed in a straight line, it will remain at rest or keep moving in a straight line at constant speed unless it is acted upon by a force . The law of inertia was first formulated by Galileo Galilei for horizontal motion on Earth and was later generalized by René Descartes . Before Galileo it had been thought that all horizontal motion required a direct cause, but Galileo deduced from his experiments that a body in motion would remain in motion unless a force (such as friction ) caused it to come to rest. This law is also the first of Isaac Newton’s three laws of motion .

Although the principle of inertia is the starting point and the fundamental assumption of classical mechanics , it is less than intuitively obvious to the untrained eye. In Aristotelian mechanics, and in ordinary experience, objects that are not being pushed tend to come to rest. The law of inertia was deduced by Galileo from his experiments with balls rolling down inclined planes.

For Galileo, the principle of inertia was fundamental to his central scientific task: he had to explain how it is possible that, if Earth is really spinning on its axis and orbiting the Sun , we do not sense that motion. The principle of inertia helps to provide the answer: since we are in motion together with Earth, and our natural tendency is to retain that motion, Earth appears to us to be at rest. Thus, the principle of inertia, far from being a statement of the obvious, was once a central issue of scientific contention . By the time Newton had sorted out all the details, it was possible to accurately account for the small deviations from this picture caused by the fact that the motion of Earth’s surface is not uniform motion in a straight line. In the Newtonian formulation, the common observation that bodies that are not pushed tend to come to rest is attributed to the fact that they have unbalanced forces acting on them, such as friction and air resistance. In classical Newtonian mechanics, there is no important distinction between rest and uniform motion in a straight line: they may be regarded as the same state of motion seen by different observers, one moving at the same velocity as the particle and the other moving at constant velocity with respect to the particle.

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for a link to the full collection. Subjects Levels Resource Types Classical Mechanics General Physics Appropriate Courses Categories Ratings Rated by 2 people Want to rate this material? Primary Details Standards (19) Next Generation Science Standards Disciplinary core ideas (k-12). The motion of an object is determined by the sum of the forces acting on it; if the total force on the object is not zero, its motion will change. The greater the mass of the object, the greater the force needed to achieve the same change in motion. For any given object, a larger force causes a larger change in motion. (6-8) Crosscutting Concepts (K-12) Much of science deals with constructing explanations of how things change and how they remain stable. (9-12) Science assumes the universe is a vast single system in which basic laws are consistent. (9-12) Scientific knowledge is based on the assumption that natural laws operate today as they did in the past and they will continue to do so in the future. (9-12) NGSS Science and Engineering Practices (K-12) Analyze data using tools, technologies, and/or models (e.g., computational, mathematical) in order to make valid and reliable scientific claims or determine an optimal design solution. (9-12) Construct an explanation based on valid and reliable evidence obtained from a variety of sources (including students' own investigations, models, theories, simulations, peer review) and the assumption that theories and laws that describe the natural world operate today as they did in the past and will continue to do so in the future. (9-12) Plan and conduct an investigation individually and collaboratively to produce data to serve as the basis for evidence, and in the design: decide on types, how much, and accuracy of data needed to produce reliable measurements and consider limitations on the precision of the data (e.g., number of trials, cost, risk, time), and refine the design accordingly. (9-12) NGSS Nature of Science Standards (K-12) Analyzing data in 9–12 builds on K–8 and progresses to introducing more detailed statistical analysis, the comparison of data sets for consistency, and the use of models to generate and analyze data. (9-12) Constructing explanations and designing solutions in 9–12 builds on K–8 experiences and progresses to explanations and designs that are supported by multiple and independent student-generated sources of evidence consistent with scientific ideas, principles, and theories. (9-12) Planning and carrying out investigations in 9-12 builds on K-8 experiences and progresses to include investigations that provide evidence for and test conceptual, mathematical, physical, and empirical models. (9-12) AAAS Benchmark Alignments (2008 Version) 1. the nature of science. 9-12: 1B/H4. There are different traditions in science about what is investigated and how, but they all share a commitment to the use of logical arguments based on empirical evidence. 2. The Nature of Mathematics 9-12: 2B/H3. Mathematics provides a precise language to describe objects and events and the relationships among them. In addition, mathematics provides tools for solving problems, analyzing data, and making logical arguments. 4. The Physical Setting 6-8: 4F/M3a. An unbalanced force acting on an object changes its speed or direction of motion, or both. 9-12: 4F/H8. Any object maintains a constant speed and direction of motion unless an unbalanced outside force acts on it. 9. The Mathematical World 6-8: 9B/M3. Graphs can show a variety of possible relationships between two variables. As one variable increases uniformly, the other may do one of the following: increase or decrease steadily, increase or decrease faster and faster, get closer and closer to some limiting value, reach some intermediate maximum or minimum, alternately increase and decrease, increase or decrease in steps, or do something different from any of these. 9-12: 9B/H4. Tables, graphs, and symbols are alternative ways of representing data and relationships that can be translated from one to another. 12. Habits of Mind 6-8: 12C/M5. Analyze simple mechanical devices and describe what the various parts are for; estimate what the effect of making a change in one part of a device would have on the device as a whole. This resource is part of a Physics Front Topical Unit. A set of seven experiments on the Law of Inertia, developed by a team of scientists and educators in the UK.  Each experiment has been classroom-tested and focuses on practical applications of the concepts to be presented.  Contains full instructions for set-up, safety information, and tips for teachers. Physical Sciences K-8 Newton's First Law & Inertia Unit Physics First Newton's First Law & Inertia Unit Conceptual Physics Newton's First Law & Inertia Unit Algebra-Based Physics Newton's First Law & Inertia Unit Citation Formats %Q Nuffield Curriculum Centre %T Practical Physics: Inertia and Newton's First Law %D October 20, 2008 %U https://spark.iop.org/collections/inertia-and-newtons-first-law %O text/html %0 Electronic Source %A Nuffield Curriculum Centre, %D October 20, 2008 %T Practical Physics: Inertia and Newton's First Law %V 2024 %N 11 August 2024 %8 October 20, 2008 %9 text/html %U https://spark.iop.org/collections/inertia-and-newtons-first-law The AIP Style presented is based on information from the AIP Style Manual . The APA Style presented is based on information from APA Style.org: Electronic References . The Chicago Style presented is based on information from Examples of Chicago-Style Documentation . The MLA Style presented is based on information from the MLA FAQ . Shared Folders (32) This resource is stored in 32 shared folders. You must login to access shared folders. Related Materials (1) Practical physics: inertia and newton's first law :. This is the full collection of Practical Physics experiments. Supplements Make a Comment Relate this resource Contact us Related Materials Practical Physics See details... Similar Materials PhysClips: Newton's Laws Teach Engineering: Energy of Motion Physics Teaching Technology Resource: Learning Cycles on Newton Suggested Searches Climate Change Expedition 64 Mars perseverance SpaceX Crew-2 International Space Station View All Topics A-Z Humans in Space Earth & climate, the solar system, the universe, aeronautics, learning resources, news & events. 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Grade Levels Grades 9-12 Other Multimedia, Videos This NASA video segment explores how Newton’s first law of motion applies to aerospace. An instructor at NASA’s National Test Pilot School defines the law of inertia and then explains how the seatbelt in a jet provides an outside force to stop the inertia of the pilot. The instructor also discusses inertia experienced by humans while riding in the test vehicles for space travel. The Law of Inertia: Newton’s First Law Duration: 3 minutes 7 seconds View on YouTube More videos and video clips in this series: Introduction to Newton’s Three Laws, Lesson 1 Force Equals Mass Times Acceleration: Newton’s Second Law The Law of Action and Reaction: Newton’s Third Law Weight and Balance, Lesson 2 Lift and Rate of Change of Momentum, Lesson 3 Drag, Lesson 4 Thrust, Lesson 5 Take Off, Lesson 6 Climb and Descent, Lesson 7 Cruise, Lesson 8 The Landing, Lesson 9 The Landing: Approach The Landing: Flare The Landing: Rollout The Landing: Summary Flight Testing Newton’s Laws Main Page Advertisement How Newton's Laws of Motion Work Share Content on Facebook Share Content on LinkedIn Share Content on Flipboard Share Content on Reddit Share Content via Email Next to E = mc ² , F = ma is the most famous equation in all of physics. Yet many people remain mystified by this fairly simple algebraic expression. It's actually a mathematical representation of Isaac Newton 's second law of motion, one of the great scientist's most important contributions. The "second" implies that other laws exist, and, luckily for students and trivia hounds everywhere, there are only two additional laws of motion. Here they are : Every object persists in its state of rest or uniform motion — in a straight line unless it is compelled to change that state by forces impressed on it. Force is equal to the change in momentum per change in time. For a constant mass , force equals mass times acceleration. For every action, there is an equal and opposite reaction. These three laws form the foundation of what is known as classical mechanics , or the science concerned with the motion of bodies related to the forces acting on it. The bodies in motion could be large objects, such as orbiting moons or planets, or they could be ordinary objects on Earth's surface, such as moving vehicles or speeding bullets. Even bodies at rest are fair game. Where classical mechanics begins to fall apart is when it tries to describe the motion of very small bodies, such as electrons. Physicists had to create a new paradigm, known as quantum mechanics , to describe the behavior of objects at the atomic and subatomic level. But quantum mechanics is beyond the scope of this article. Our focus will be classical mechanics and Newton's three laws . We'll examine each in detail, both from a theoretical and a practical point of view. We'll also discuss the history of Newton's laws , because how he arrived at his conclusions is just as important as the conclusions themselves. The best place to start, of course, is at the beginning with Newton's first law. Newton's First Law (Law of Inertia) A brief history of newton's laws, newton's second law (law of motion), newton's third law (law of force pairs), applications and limitations of newton's laws. Let's restate Newton's first law in everyday terms: The "forever" part is difficult to swallow sometimes. But imagine that you have three ramps set up as shown below. Also imagine that the ramps are infinitely long and infinitely smooth. You let a marble roll down the first ramp, which is set at a slight incline. The marble speeds up on its way down the ramp. Now, you give a gentle push to the marble going uphill on the second ramp. It slows down as it goes up. Finally, you push a marble on a ramp that represents the middle state between the first two — in other words, a ramp that is perfectly horizontal. In this case, the marble will neither slow down nor speed up. In fact, it should keep rolling. Forever. Physicists use the term inertia to describe this tendency of an object to resist a change in its motion. The Latin root for inertia is the same root for "inert," which means lacking the ability to move. So, you can see how scientists came up with the word. What's more amazing is that they came up with the concept. Inertia isn't an immediately apparent physical property, such as length or volume. It is, however, related to an object's mass. To understand how, consider the sumo wrestler and the boy shown below. Let's say the wrestler on the left has a mass of 136 kilograms, and the boy on the right has a mass of 30 kilograms (scientists measure mass in kilograms). Remember the object of sumo wrestling is to move your opponent from his position. Which person in our example would be easier to move? Common sense tells you that the boy would be easier to move, or less resistant to inertia. You experience inertia in a moving car all the time. In fact, seat belts exist in cars specifically to counteract the effects of inertia. Imagine for a moment that a car at a test track is traveling at a speed of 55 mph (80 kph). Now imagine that a crash test dummy is inside that car, riding in the front seat. If the car slams into a wall, the dummy flies forward into the dashboard. Why? Because, according to Newton's first law, an object in motion will remain in motion until an outside force acts on it. When the car hits the wall, the dummy keeps moving in a straight line and at a constant speed until the dashboard applies a force. Seatbelts hold dummies (and passengers) down, protecting them from their own inertia. Interestingly, Newton wasn't the first scientist to come up with the law of inertia. That honor goes to Galileo and to René Descartes. In fact, the marble-and-ramp thought experiment described previously is credited to Galileo. Newton owed much to events and people who preceded him. Before we continue with his other two laws, let's review some of the important history that informed them. The Greek philosopher Aristotle dominated scientific thinking for many years. His views on motion were widely accepted because they seemed to support what people observed in nature. For example, Aristotle thought that weight affected falling objects. A heavier object, he argued, would reach the ground faster than a lighter object dropped at the same time from the same height. He also rejected the notion of inertia, asserting instead that a force must be constantly applied to keep something moving. Both of these concepts were wrong, but it would take many years — and several daring thinkers — to overturn them. The first big blow to Aristotle's ideas came in the 16th century when Nicolaus Copernicus published his sun-centered model of the universe. Aristotle theorized that the sun , the moon and the planets all revolved around Earth on a set of celestial spheres. Copernicus proposed that the planets of the solar system revolved around the sun, not Earth. Although not a topic of mechanics per se, the heliocentric cosmology described by Copernicus revealed the vulnerability of Aristotle's science. Galileo Galilei was the next to challenge the Greek philosopher's ideas. Galileo conducted two now-classic experiments that set the tone and tenor for all scientific work that would follow. In the first experiment, he dropped a cannonball and a musket ball from the Leaning Tower of Pisa. Aristotelian theory predicted that the cannonball, much more massive, would fall faster and hit the ground first. But Galileo found that the two objects fell at the same rate and struck the ground roughly at the same time. Some historians question whether Galileo ever carried out the Pisa experiment, but he followed it with a second phase of work that has been well-documented. These experiments involved bronze balls of various sizes rolling down an inclined wood plane. Galileo recorded how far a ball would roll in each one-second interval. He found that the size of the ball didn't matter — the rate of its descent along the ramp remained constant. From this, he concluded that freely falling objects experience uniform acceleration regardless of mass, as long as extraneous forces, such as air resistance and friction, can be minimized. But it was René Descartes, the great French philosopher, who would add new depth and dimension to inertial motion. In his "Principles of Philosophy," Descartes proposed three laws of nature. The first law states that each thing, as far as is in its power, always remains in the same state; and that consequently, when it is once moved, it always continues to move. The second holds that all movement is, of itself, along straight lines. This is Newton's first law, clearly stated in a book published in 1644 — when Newton was still a newborn! Clearly, Isaac Newton studied Descartes. He put that studying to good use as he single-handedly launched the modern era of scientific thinking. Newton's work in mathematics resulted in integral and differential calculus. His work in optics led to the first reflecting telescope. And yet his most famous contribution came in the form of three relatively simple laws that could be used, with great predictive power, to describe the motion of objects on Earth and in the heavens. The first of these laws came directly from Descartes, but the remaining two belong to Newton alone. He described all three in "The Mathematical Principles of Natural Philosophy," or the Principia, which was published in 1687. Today, the Principia remains one of the most influential books in the history of human existence. Much of its importance lies within the elegantly simple second law, F = ma , which is the topic of the next section. You may be surprised to learn that Newton wasn't the genius behind the law of inertia. But Newton himself wrote that he was able to see so far only because he stood on "the shoulders of Giants." And see far he did. Although the law of inertia identified forces as the actions required to stop or start motion, it didn't quantify those forces. Newton's second law supplied the missing link by relating force to acceleration. This is what it said: Technically, Newton equated force to the differential change in momentum per unit time. Momentum is a characteristic of a moving body determined by the product of the body's mass and velocity. To determine the differential change in momentum per unit time, Newton developed a new type of math — differential calculus. His original equation looked something like this: F = (m)(Δv/Δt) where the delta symbols signify change. Because acceleration is defined as the instantaneous change in velocity in an instant of time (Δv/Δt), the equation is often rewritten as: The F , the m and the a in Newton's formula are very important concepts in mechanics. The F is force , a push or pull exerted on an object. The m is mass , a measure of how much matter is in an object. And the a is acceleration, which describes how an object's velocity changes over time. Velocity , which is similar to speed, is the distance an object travels in a certain amount of time. The equation form of Newton's second law allows us to specify a unit of measurement for force. Because the standard unit of mass is the kilogram (kg) and the standard unit of acceleration is meters per second squared (m/s 2 ), the unit for force must be a product of the two — (kg)(m/s 2 ). This is a little awkward, so scientists decided to use a Newton as the official unit of force. One Newton, or N, is equivalent to 1 kilogram-meter per second squared. There are 4.448 N in 1 pound. So, what can you do with Newton's second law? As it turns out, F = ma lets you quantify motion of every variety. Let's say, for example, you want to calculate the acceleration of the dog sled shown at left. Now let's say that the mass of the sled stays at 50 kilograms and that another dog is added to the team. If we assume the second dog pulls with equal force to the first (100 N), the total force would be 200 N and the acceleration would be 4 m/s 2 . However, doubling the mass to 100 kilograms would halve the acceleration to 2 m/s 2 . Finally, let's imagine that a second dog team is attached to the sled so that it can pull in the opposite direction. This is important because Newton's second law is concerned with net forces. We could rewrite the law to say: When a net force acts on an object, the object accelerates in the direction of the net force. Now imagine that one of the dogs on the left breaks free and runs away. Suddenly, the force pulling to the right is larger than the force pulling to the left, so the sled accelerates to the right. What's not so obvious in our examples is that the sled is also applying a force on the dogs. In other words, all forces act in pairs. This is Newton's third law — and the topic of the next section. Newton's third law is probably the most familiar. Everyone knows that every action has an equal and opposite reaction, right? Unfortunately, this statement lacks some necessary detail. This is a better way to say it: Many people have trouble visualizing this law because it's not as intuitive. In fact, the best way to discuss the law of force pairs is by presenting examples. Let's start by considering a swimmer facing the wall of a pool. If she places her feet on the wall and pushes hard, what happens? She shoots backward, away from the wall. Clearly, the swimmer is applying a force to the wall, but her motion indicates that a force is being applied to her, too. This force comes from the wall, and it's equal in magnitude and opposite in direction. Next, think about a book lying on a table. What forces are acting on it? One big force is Earth's gravity. In fact, the book's weight is a measurement of Earth's gravitational attraction. So, if we say the book weighs 10 N, what we're really saying is that Earth is applying a force of 10 N on the book. The force is directed straight down, toward the center of the planet. Despite this force, the book remains motionless, which can only mean one thing: There must be another force, equal to 10 N, pushing upward. That equal and opposite force is coming from the table. If you're catching on to Newton's third law, you should have noticed another force pair described in the paragraph above. Earth is applying a force on the book, so the book must be applying a force on Earth. Is that possible? Yes, it is, but the book is so small that it cannot appreciably accelerate something as large as a planet. You see something similar, although on a much smaller scale, when a baseball bat strikes a ball. There's no doubt the bat applies a force to the ball: It accelerates rapidly after being struck. But the ball must also be applying a force to the bat. The mass of the ball, however, is small compared to the mass of the bat, which includes the batter attached to the end of it. Still, if you've ever seen a wooden baseball bat break into pieces as it strikes a ball, then you've seen firsthand evidence of the ball's force. These examples don't show a practical application of Newton's third law. Is there a way to put force pairs to good use? Jet propulsion is one application. Used by animals such as squid and octopuses , as well as by certain airplanes and rockets, jet propulsion involves forcing a substance through an opening at high speed. In squid and octopuses, the substance is seawater, which is sucked in through the mantle and ejected through a siphon. Because the animal exerts a force on the water jet, the water jet exerts a force on the animal, causing it to move. A similar principle is at work in turbine-equipped jet planes and rockets in space. Speaking of outer space, Newton's other laws apply there, too. By using his laws to analyze the motion of planets in space, Newton was able to come up with a universal law of gravitation. By themselves, the three laws of motion are a crowning achievement, but Newton didn't stop there. He took those ideas and applied them to a problem that had stumped scientists for years: the motion of planets. Copernicus placed the sun at the center of a family of orbiting planets and moons, while the German astronomer Johannes Kepler proved that the shape of planetary orbits was elliptical, not circular. But no one had been able to explain the mechanics behind this motion. Then, as the story goes, Newton saw an apple fall to the ground and was seized by inspiration. Could a falling apple be related to a revolving planet or moon? Newton believed so. This was his thought process to prove it: An apple falling to the ground must be under the influence of a force, according to his second law. That force is gravity, which causes the apple to accelerate toward Earth's center. Newton reasoned that the moon might be under the influence of Earth's gravity, as well, but he had to explain why the moon didn't fall into Earth. Unlike the falling apple, it moved parallel to Earth's surface. What if, he wondered, the moon moved about Earth in the same way as a stone whirled around at the end of a string? If the holder of the string let go — and therefore stopped applying a force — the stone would obey the law of inertia and continue traveling in a straight line, like a tangent extending from the circumference of the circle. But if the holder of the string didn't let go, the stone would travel in a circular path, like the face of a clock. In one instant, the stone would be at 12 o'clock. In the next, it would be at 3 o'clock. A force is required to pull the stone inward so it continues its circular path or orbit. The force comes from the holder of the string. Next, Newton reasoned that the moon orbiting Earth was the same as the stone whirling around on its string. Earth behaved as the holder of the string, exerting an inward-directed force on the moon. This force was balanced by the moon's inertia, which tried to keep the moon moving in a straight-line tangent to the circular path. Finally, Newton extended this line of reasoning to any of the planets revolving around the sun. Each planet has inertial motion balanced by a gravitational attraction coming from the center of the sun. It was a stunning insight — one that eventually led to the universal law of gravitation. According to this law, any two objects in the universe attract each other with a force that depends on two things: the masses of the interacting objects and the distance between them. More massive objects have bigger gravitational attractions. Distance diminishes this attraction. Newton expressed this mathematically in this equation: F = G(m1m2/r 2 ) where F is the force of gravity between masses m1 and m2 , G is a universal constant and r is the distance between the centers of both masses. Over the years, scientists in just about every discipline have tested Newton's laws of motion and found them to be amazingly predictive and reliable. But there are two instances where Newtonian physics break down. The first involves objects traveling at or near the speed of light. The second problem comes when Newton's laws are applied to very small objects, such as atoms or subatomic particles that fall in the realm of quantum mechanics. Lots More Information Related articles. How Isaac Newton Worked How Time Works 10 Isaac Newton Inventions How Special Relativity Works How Warp Speed Works More Great Links Newton's Laws of Motion on NASA Newton's Laws of Motion: In Our Time, BBC Radio Barnes-Svarney, Patricia, Ed. "The New York Public Library Science Desk Reference." Macmillan. 1995. Crowther, J.G. "Six Great Scientists." Barnes & Noble Books. 1995. Dennis, Johnnie T. "The Complete Idiot's Guide to Physics." Alpha Books. 2003. Encyclopædia Britannica 2005, s.v. "Mechanics." CD-ROM, 2005. Encyclopædia Britannica 2005, s.v. "Newton's laws of motion." CD-ROM, 2005. Encyclopædia Britannica 2005, s.v. "Newton, Sir Isaac." CD-ROM, 2005. Gundersen, P. Erik. "The Handy Physics Answer Book." Visible Ink Press. 2003. Hobson, Art. "Physics: Concepts & Connections, Fourth Edition." Pearson Prentice Hall. 2007. Johnson, George. "The Ten Most Beautiful Experiments." Alfred A. Knopf. 2008. NASA. "Newton's Laws of Motion." Glenn Research Center. July 11, 2008. (July 21, 2008) http://www.grc.nasa.gov/WWW/K-12/airplane/newton.html NOVA. "Newton's Dark Secrets on NOVA" (July 21, 2008) http://www.pbs.org/wgbh/nova/newton/ Scien­ce Channel. "Isaac Newton's Laws of Motion: Science Channel." (July 21, 2008) http://science.discovery.com/interactives/literacy/newton/newton.html Please copy/paste the following text to properly cite this HowStuffWorks.com article: 136 IMAGES Law of INERTIA Experiment : 5 SCIENCE EXPERIMENTS for Kids Inertia example our daily lives infographic diagram experiment to Inertia in Physic Easy Inertia Science Experiments with Pennies Inertia in Physic Easy Inertia Experiment for Kids COMMENTS Easy Inertia Experiment This inertia experiment is super easy and a great fun science trick for kids and adults! If you want to learn more about Isaac Newton's Laws of Motion or Simple Science Experiments: Newton's First Law of Motion Many years ago, Sir Isaac Newton came up with some most excellent descriptions about motion. Here are a couple of experiments that demonstrate this very cool law of motion; in a word called "inertia." Newton's First Law Experiment Inertia is an object's resistance to change in its state of motion, whether at rest or moving. Objects retain their inertia unless acted on by a force. Force can be applied in many ways. Try this simple experiment to test Newton's first law of motion. It will help you and your students get a good idea of what the Law Of Inertia is all about ... 4.2 Newton's First Law of Motion: Inertia Learn how Newton's first law of motion explains the concept of inertia and the relationship between force and motion in this OpenStax Physics chapter. Inertia Science Experiment Try this easy science experiment at home with a glass of water, a paper plate, a cardboard tube, a broomstick, and an egg. 🧑‍🔬How does it work? An object a... What is Newton's first law? (article) What does mass mean? The property of a body to remain at rest or to remain in motion with constant velocity is called inertia. Newton's first law is often called the law of inertia. As we know from experience, some objects have more inertia than others. Inertia and Newton's first law Inertia with pendulums Practical Activity for 14-16 Demonstration The tendency of a body to resist acceleration is called its inertia. This experiment provides direct experience of applying force and experiencing inertia. 4.2 Newton's First Law of Motion: Inertia The property of a body to remain at rest or to remain in motion with constant velocity is called inertia. Newton's first law is often called the law of ... Newtons First Law Inertia with pendulums Demonstration: The tendency of a body to resist acceleration is called its inertia. This experiment provides direct experience... Practical Activity 14-16 Newton's First Law Forces and Motion Easy Inertia Science Experiments with Pennies Two fun and hands-on inertia science experiments that will teach kids all about the concept of inertia and Newton's First Law of Motion. What is Inertia and how to demonstrate it Learn about Inertia and Newton's laws, one of the core principles in Physics. Also, see how to demonstrate Inertia with a simple experiment. Newton's First Law of Motion The focus of Lesson 1 is Newton's first law of motion - sometimes referred to as the law of inertia. Newton's first law of motion is often stated as. An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force. Simple Inertia experiments This video contains five easy demonstration on inertia properties of matter. These experiments can be done at home or at school easily. Home Experiment: Newton's First Law/Law of Inertia Home Experiment: Newton's First Law/Law of Inertia: This is a variation of the classic pulling out the table cloth experiment. The pen cap can be substituted for anything small enough to fit inside of the bottle's neck. If you find it difficult, you can try using something that is shorter, such as a …. Law of inertia Law of inertia, postulate in physics that, if a body is at rest or moving at a constant speed in a straight line, it will remain at rest or keep moving in a straight line at constant speed unless it is acted upon by a force. This law is also the first of Isaac Newton's three laws of motion. Practical Physics: Inertia and Newton's First Law This is a set of six introductory experiments on the Law of Inertia, developed for use in high school science classrooms. Each experiment focuses on practical applications of Newton's First Law, and is supplemented with full instructional guidelines, drawings/photos, and tips for teachers. Especially noteworthy are the links to lab safety ... Home Experiment: Newton's First Law/Law of Inertia This is a variation of the classic pulling out the table cloth experiment. The pen cap can be substituted for anything small enough to fit inside of the bott... The Law of Inertia: Newton's First Law This NASA video segment explores how Newton's first law of motion applies to aerospace. An instructor at NASA's National Test Pilot School defines the law of inertia and then explains how the seatbelt in a jet provides an outside force to stop the inertia of the pilot. The instructor also discusses inertia experienced by humans while riding ... How Newton's Laws of Motion Work Although the law of inertia identified forces as the actions required to stop or start motion, it didn't quantify those forces. Newton's second law supplied the missing link by relating force to acceleration. Newton's laws of motion Newton's first law expresses the principle of inertia: the natural behavior of a body is to move in a straight line at constant speed. A body's motion preserves the status quo, but external forces can perturb this. The modern understanding of Newton's first law is that no inertial observer is privileged over any other. Inertia in Physic On this page we will learn about law of inertia in physics, inertia and types of inertia. But before going any further on the topic we shall learn about the the Galileo's experiment on motion of objects. Let us first begin with the Galileo's experiments on the motion of objects and how he defined inertia and law of inertia. essay homework paper phd project resume review speech thesis