A2L Item 157
- Description: Identify the correct statement about the impulse on two blocks due to the gravitational force.
- Goal: Hone the concept of impulse
- Source: UMPERG-ctqpe86
- Keywords: Impulse, Mechanics
The question for students:
The
two blocks shown below are identical. In case A the block sits on a
horizontal surface and in case B the block is in free fall. Which
statement is correct regarding the impulse delivered to the block by the
gravitational force during a time interval Δt?
- In case A the impulse is zero.
- In case B the impulse depends upon v.
- The impulse is larger in case B than A.
- None of the above
- Cannot be determined
Commentary for teachers:
Answer
(4) Even students who understand forces and would respond correctly to this question if asked in terms of forces have difficulty with this question. Many think that motion matters, or answer the question as if it was about the net impulse.