The kinetic energy of the bob on a simple pendulum swinging in simple harmonic motion has its maximum value when the displacement from equilibrium is at what point in its swing?

a. zero displacement
b. 1/4 the amplitude
c. 1/2 the amplitude
d. equals the amplitude

A. Zero displacement.

Explanation:

The kinetic energy of the bob is directly proportional to its velocity. The velocity of the bob in simple harmonic motion is at the position where its potential energy is minimum, in this case zero. When the bob is at the equilibrium, its potential energy is zero, and its velocity is maximum.

Conversely, when it is at the amplitude, its velocity is zero.

acceleration = (change in speed) / (time for the change)

change in speed = (20-120)= -100 m/s.

1.5 min = 90 sec

acceleration = -100/90 = -1.11 m/s^2.

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