A2L Item 131

Goal: Reasoning with dynamics

Source: UMPERG-ctqpe30

A
block of mass m, when placed on a rough inclined plane and moved, moves
down the plane with constant speed. If a block of mass 2m were placed
on the same incline and moved, it would …

  1. return to rest.
  2. accelerate until the speed is half.
  3. move with some constant speed.
  4. None of the above.
  5. Cannot be determined

Commentary:

Answer

The block will have the same motion. Both the gravitational force
and the friction force scale with the mass so there is no net force in
either case.