**Goal:** Translate between representations of motion

**Source:** UMPERG

The strobe diagram below shows the position of an object at successive

equal time intervals. The object moves from left to right.

Consider the following situations:

A. A book slides down an incline, moving from a rough region onto a

smooth region.

B. A cart is connected to a compressed spring and released.

C. A ball is dropped, hits the ground and rebounds to its initial

position.

D. A runner runs a race.

Which of these situations could be roughly described by the strobe

diagram?

- A
- B
- C
- D
- A & B
- C & D
- B & D
- A, B, C & D
- None of the above

## Commentary:

## Answer

(2),(4) or (7); Depending upon assumptions (B) or (D) are possible. The cart leaving the spring would speed up then eventually slow down due to friction. Also, the runner will speed up and eventually slow down.