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A2L Item 145

Meta-Information
Description: 
Compare the final speed of two masses traveling down different surfaces.
Goal: 
Reasoning with energy
Level: 
High School
Level: 
Undergraduate
Keywords: 
Conservation
Keywords: 
Energy
Keywords: 
Mechanics
Keywords: 
Velocity
Source: 
UMPERG-ctqpe64

Two masses, M > m, travel down the surfaces shown. Both surfaces are frictionless. Which mass has the largest speed at the bottom?

  1. m
  2. M
  3. Both have the same speed
  4. Cannot be determined
Commentary

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.