In the diagram below, A, B, C, D are four pendulums suspended from the same elastic string PQ. The length of A and Care equal to each other while the length of pendulum B is smaller than that of D. Pendulum A is set into a mode of vibrations.

State the reason for the type of vibrations in pendulums B and C.

Explanation

This is because the time period of pendulum B is different from that of C (since length of the pendulums B and C are different).