Question

When the maximum kinetic energy of a simple pendulum is K, then what its displacement (in terms of amplitude a) when its kinetic energy is K/2?

(a) a/√2

(b) a/2

(c) a/√3

(d) a/3

The question was asked during an interview.

The doubt is from Harmonic Motion topic in portion Oscillations of Engineering Physics I

Answer 1

Correct choice is (a) a/√2

To explain: Here Kmax=1/2×ka^2=K

Let

1/2×ky^2=K/2=1/2×1/2×ka^2

y=a/√2.