Key Concepts
What is Newton's third law of motion?
What is needed for an object to have a large momentum?
How is momentum conserved?
Vocabulary
momentum
law of conservation of momentum
Reading Strategy
Summarizing Read the section on momentum. Then copy and complete the concept map below to organize what you know about momentum.
Think physics the next time you go to an amusement park. There is no better place than an amusement park to see Newton's laws in action. As you experience sudden starts, stops, changes in direction, and possibly even free fall, you can be sure that the laws of physics control your motion. The bumper cars in Figure 15 illustrate momentum and Newton's third law of motion, the subjects of this section.
If you have ever driven a bumper car, you know your goal is to slam into another car head on. When you collide with the other car, you do so with enough force to jolt the other driver almost out of the seat. There are two parts to this collision, however—the collision also causes your own car to rebound sharply. Newton's third law of motion explains the behavior of the bumper cars during a collision.
Figure 15 When this bumper car collides with another car, two forces are exerted. Each car in the collision exerts a force on the other.