Question

In the diagram below, A, B, C, D are four pendulums suspended from the same elastic string PQ. The length of A and C are 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.

(i) Name the type of vibrations taking place in pendulums B and D ? 

(ii) What is the state of pendulum C ? 

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

Answer 1

(i) B and D would be in the state of force vibration. 

(ii) Since the length of pendulum C is same as that of A therefore it is in the state of resonance. 

(iii) The pendulum C has its length same as that of A therefore its natural time period is also same that of A and both remain in same phase so resonance takes place. But B’s length is lesser than the length of A hence B would vibrate with smaller amplitude.