Simple Harmonic Motion - Multiple Choice Questions

Q11. Which one of the following statements always applies to a damping force acting on a vibrating system?

A It is in the same direction as the acceleration.
B It is in the same direction as the displacement.
C It is in the opposite direction to the velocity.
D It is proportional to the displacement.

The damping force is a frictional force - it opposes motion - it is therefore ALWAYS in the opposite direction to velocity.