Four pendulums A, B, C and D are suspended from the same elastic support as shown in figure. [NCERT Exemplar]A and C are of the same length, while B is smaller than A and D is larger than A. If A is given a transverse displacement,

According to the question, A is given a transverse displacement.Through the elastic support, the disturbance is transferred to all the pendulums.A and C are having same length, hence they will be in resonance, because their time period of oscillation,                        T = 2πlgand hence, frequency will be same.So, amplitude of C will be maximum.Note In this problem, we have assumed that the support is perfectly elastic and there is no damping. Hence, oscillation is considered as undamped.