A2L Item 145
- Description: Compare the final speed of two masses traveling down different surfaces.
- Goal: Reasoning with energy
- Source: UMPERG-ctqpe64
- Keywords: Conservation, Energy, Mechanics, Velocity
The question for students:
Two
masses, M > m, travel down the surfaces shown. Both surfaces are
frictionless. Which mass has the largest speed at the bottom?
- m
- M
- Both have the same speed
- Cannot be determined
Commentary for teachers:
Answer
(3) By energy considerations, both would have the same speed. Students frequently get confused about the mass, thinking that the larger mass has the greatest potential energy change and therefore has the greatest speed.