Description
Impulse and work both come from a net force, but they measure different things: force over time changes momentum, and force over distance changes kinetic energy. In this AP Physics C: Mechanics video, we stop a linebacker and a wide receiver with the same force and find the time and the distance for each. Then we choose between the impulse–momentum theorem and the work–energy theorem for forces that depend on time or on position, and explain how a spring bumper can deliver an impulse while doing zero net work.
In this video:
0:00 Hook: stopping the linebacker and the receiver
1:24 Two ways a force changes motion
2:19 Which theorem do I use?
2:32 Example: stopping the players (time and distance)
6:04 Example: force as a function of time or position
9:34 Example: spring bumper (zero work, nonzero impulse)
12:33 Preview: changing mass
Download the guided notes and practice problems for this unit at houstonscience.com.
Part of the AP Physics C: Mechanics Unit 4 (Linear Momentum) series.