(i) Frequency f of the simple pendulum :
Hence frequency is inversely proportional to square root of length. Pendulam-C will have maximum frequency
Pendulam-A will have minimum frequency
(ii) If Pendula-A starts vibrating , all remaining pendulams B , C and D will be vibrating
Vibrations of pendulam-A :- natural vibration
(iii) If Pendula-D starts vibrating , all remaining pendulams A, B and C will be vibrating
Vibrations of pendulam A, B and C :- forced vibration