Description
What happens to momentum and force when mass is added to or removed from a moving system? In this AP Physics C: Mechanics video, we use the product rule to write dp/dt = m dv/dt + v dm/dt, then apply F = v dm/dt when mass changes at constant velocity. Examples include sand falling onto a conveyor belt, a fire extinguisher, and rocket thrust, and we use Newton’s third law to find the thrust and reaction forces. We finish by summarizing all of 4.2 and previewing conservation of momentum.
In this video:
0:00 Hook: sand on a conveyor belt
0:55 The product rule and momentum when mass changes
2:43 Example: conveyor belt
3:32 Example: fire extinguisher
4:32 Example: rocket thrust
6:25 The big picture for 4.2
7:58 Preview: conservation of momentum
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.