Question

The image shows a pendulum in simple harmonic motion. The pendulum starts at A and swings to E.

An illustration of a pendulum at 5 different positions. The central position, the equilibrium position is labeled C. The two positions on the left are labeled a and B respectively. The two positions on the right are labeled D and E respectively. All positions are equally spaced.
Which labels are correct? Check all that apply.

E: Net force is zero.
D: Velocity is decreasing. Acceleration is increasing.
A: Velocity is zero.
C: Acceleration is maximum.
B: Velocity is decreasing. Net force is decreasing.
E: Velocity is maximum.

Answer 1

Correct: A and D.

Brief reasons:
- A: True — at the leftmost extreme the bob is momentarily at rest (v = 0).
- D: True — after passing the centre the bob is slowing down (v decreasing) and the restoring acceleration (its magnitude) grows as it approaches the right extreme.
- B: False — at B the bob is speeding up toward the centre, though the net restoring force magnitude is decreasing.
- C: False — at the centre acceleration is zero (not maximum).
- E (both statements): False — at the rightmost extreme velocity is zero and the restoring force is large (not zero).