**Goal:** Problem solving

**Source:** UMPERG-ctqpe84

A mass of 0.5 kg moving along a horizontal frictionless surface

encounters a spring having k = 200 N/m. The mass compresses the spring

by 0.1 meters before reversing its direction. Consider the total time

the mass is in contact with the spring. What is the total impulse

delivered to the mass by the spring?

- -4 N-s
- -2 N-s
- 0 N-s
- 2 N-s
- 4 N-s
- none of the above
- cannot be determined.

## Commentary:

## Answer

(2) This problem requires students to put together the concepts

of kinetic and potential energy, and change of momentum. Some may be

tempted to resort to the definition of impulse and try to determine the

force due to the spring.