Description
When is momentum conserved? It depends on the system you choose. In this AP Physics C: Mechanics video, we define a system, separate internal from external forces, and use Newton’s third law to show that internal impulses are equal and opposite, so they cannot change a system’s total momentum. We state conservation of linear momentum (including component by component), relate a net external impulse to the change in a system’s momentum, and practice choosing a system for which momentum is constant.
In this video:
0:00 Hook: a skateboarder throws a ball
1:08 What is a system? Internal vs. external forces
1:29 Newton’s third law and internal impulses
4:12 Internal forces transfer momentum but can’t change the total
4:46 Conservation of linear momentum
5:34 Example: is p constant in the system?
7:23 Example: external impulse and system momentum
10:37 Preview: solving collision and explosion problems
Download the guided notes and practice problems for this unit at houstonscience.com.