Newtons Three Laws of Motion
Objective: Explain Newtons Three Laws of Motion and give examples.
MatchCard: Download below.
Students will identify the three different laws of motion and place the descriptions and examples in the correct box.
Projects: Play marbles, soccer, or other ball games to demonstrate the 3 Laws of Motion.
Download and Use Newtons Three Laws MatchCard
This is MatchCard #7 of the Force and Motion Unit Study. You can find more information on MatchCard Science below.
Sports and games with balls are a practical way to study Newtons 3 laws of motion. Before using the MatchCard, let the students play a game of marbles.
How to Play Marbles
Here's a simple and common game of marbles. Draw a circle on the floor or in the dirt. Have an odd number of marbles randomly spread around the circle. Each player has one shooter (large) marble. The first player starts with his/her marble outside of the circle, and "shoots" the shooter by propelling it with the thumb towards a marble. When players send one of the regular marbles out of the circle, they get to keep that marble, and take another turn. Their turn ends when their shooter does not send a marble out of the circle. The winner is the person with the most marbles.
Allow the students to play the game as an introduction to the laws of motion. After the first several turns, start using the word "force" and "acceleration" as they play.
Alternatives to marbles might include:
After the game is over, tell the students that Newton's 3 laws of motion will help explain the movement of the balls in the game.
1st Law - Law of Inertia
The first of Newtons three laws is the law of inertia.
An object will continue in its direction and velocity unless it is acted on by an outside force.
Because of inertia, unmoving marbles stayed at rest until they were hit by another marble. At the same time, marbles that were moving in one direction continued to do so until a force acted upon it that either stopped the motion or changed the direction.
Note: Friction from the surface of the floor and air acted as a force as well as obstacles the marble hit.
Brainstorm other examples of inertia - particularly in sports, games, or hobbies.
Learn more about inertia and friction with this MatchCard on Inertia and Friction.
2nd Law - Force Equals Mass X Acceleration
The second law of motion describes how the force is proportional to the mass of the object and acceleration.
When a force acts on an object with mass, the object will accelerate in the direction of the force. The force is equal to the product of mass and acceleration.
The equation is written as:
F = M X A
F = Force; M = Mass; A = Acceleration
What does this mean? The harder the force, the greater the acceleration (change in speed over time.) Force and acceleration are proportional to each other.
Try it with the marbles. Give a little push, then a harder push. The greater force not only propels the marble further, but also faster.
Brainstorm other examples of force accelerating on object in games, sports, or other hobbies.
Let's look at another application of this law. With equal force, the acceleration of an object with smaller mass would be greater than an object with larger mass. If a child rolled a five pound bowling ball as hard as he or she could; and a fifteen pound bowling ball as hard as possible, which would go faster?
This MatchCard explains more about speed, velocity, momentum, and acceleration
3rd Law - Action-Reaction Law
This is probably the most frequently quoted of Newtons three laws of motion. "For every action there is an equal and opposite reaction."
We have been using the term "force", so we will stick to that.
For every force there is an opposite and equal force.
Okay, here's an illustration for this law. You see an inflated beach ball in a park and you want to kick the ball into the ball field. You run up, pull back your leg and kick it as hard as you can. Because of its light weight and your strong kick it goes soaring high and far.
Hmm, where was the equal and opposite force there? Well instead, let's suppose you ran up and kicked it as hard as you could, just like you did before. Oops, it's not an inflatable ball, but a 150 pound marble sculpture that is painted to look like a beach ball. Ouch! Do you think there might be a reaction in your toes and leg!
Note how this worked with your marble game. When one marble hit another marble, both marbles were affected. The speed and direction of the moving marble changed when it struck the marble at rest. In upper level physics, you would actually calculate the speed, distance, and effects of friction on both objects. Okay, let's just make it easier and say they are equal for now, can we?
Brainstorm other examples in sports. What happens to your arm in baseball when you catch a fast moving ball?
Watch A Game
You have played a game and discussed the three laws of motion. Now, watch a game or activity, and see how many examples you can find.
- Choose one sport or activity and describe how Newton's laws are applied. Make a video or photo display. (Soccer is a good sport to try this with - but it can be done with any activity that has movement.)
- Make a poster and include all the activities you brainstormed. Continue looking for examples of Newtons three laws of motions in your daily life.