Roll Away

SCIENCE CONCEPT:

Learning about physics can be fun and at the same time a mystery! Newton's Third Law of Motion is one of those laws that is mysterious. The Third Law states that for every action, there is an equal and opposite reaction. According to Newton, if you push against a wall, at the same time that you move away from the wall, the wall moves away from you. It's true, but the movement is too small to measure.

STUDENT OBJECTIVE:

The student will explore Newton's Third Law of Motion using roller skates and a heavy ball (basketball).

OVERVIEW:

In this activity, the student will discover how Newton's Third Law of Motion works. The student will roll backward with their roller skates. Then, the student will toss a basketball hard. The ball goes one way, and as you push the ball away, you move away in the opposite direction.

PREPARATION TIME:

5 minutes.

LESSON TIME:

20 minutes.

TEACHER PREP:

Ask students to bring their roller skates to school. Also, ask some students to bring basketballs from home.

WORDS TO KNOW:

action and reaction

equal

opposite

force

two effects

TEACHER TEXT:

If you have ever seen a film of a rocket taking off, you have watched Newton's Third Law of Motion in action. As the fuel ignites in the rocket, it starts to produce expanding gases that push out in all directions. The gases can escape only from the rear of the rocket. As the flaming gases are pushed out the rear of the rocket, the rocket is pushed skyward. This is the action - reaction that Newton discovered.

When you are in a swimming pool with a friend and you decide to race each other, you are sure to observe Newton's Third Law. When you use your arms to push the water back, the water moves in that direction, and you move forward.

When a team is rowing with oars in a boat, the flat blades of the oars push against the water. Isaac Newton pointed out that any force has two effects. In this case, when a force is exerted on the oar, it acts on the water. It also acts in an opposite direction on the boat. One force makes the water and the boat move in opposite directions. Physicists refer to this relationship of effects as 'action and reaction'. There are so many examples of Newton's Third Law all around us.

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Last modified: Wed Nov 26 10:37:56 PST 1997