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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
1) Name the type of vibrations taking place in pendulums B and D?
2) What is the state of pendulum C?
3) State the reason for the type of vibrations in pendulum B and C.
Solution
1) The vibrations which occur in pendulums B and D are called forced vibrations.
2) Pendulum C is in the state of resonance with pendulum A as it is of the same length.
3) The pendulums vibrate because the forced vibration from A is transferred due to string PQ
Pendulum B is of a different length as compared to pendulum A. Hence, it will continuously vibrate with a frequency which is different from that of pendulum A. Its amplitude will also be very small.
Pendulum C is of the same length as compared to pendulum A. Hence, it will vibrate in phase with pendulum A. Its amplitude will be equal to that of pendulum A as it will attain resonance
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