- Question Answer
- In figure, A, B, C and D are four pendulums suspended from the same elastic string XY
. In figure, A, B, C and D are four pendulums suspended from the same elastic string XY
In figure, A, B, C and D are four pendulums suspended from the same elastic string XY. Length of pendulum A and D are equal, while the length of B is smaller and C is longer. The pendulum A is set into vibrations. (a) What is your observation? (b) Give reason for your observation.
(a) Set the pendulum A into vibration by displacing it to one side, normal to its length. It is observed that pendulum D also starts vibrating initially with a small amplitude and ultimately it acquires the same amplitude as the pendulum A initially had. When the amplitude of the pendulum D becomes maximum, the amplitude of the pendulum A becomes minimum since the total energy is constant. After some time the amplitude of the pendulum D will decreases and amplitude of A increases. The exchange of energy takes place only between the pendulums A and D because their natural frequencies are same. The pendulums B and C also vibrate, but with very small amplitudes.
(b) The vibrations produced in pendulum A are communicated as forced vibrations to the other pendulums B, C and D through XY. The pendulums B and C remain in the state of forced vibrations, while the pendulum D comes in the state of resonance.