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Question
In Fig. A, B, C and D are four pendulums suspended from the same elastic string XY. The lengths of pendulum A and D are equal, while the length of pendulum B is shorter and of the pendulum C is longer. Pendulum A is set into vibrations.
- What is your observation about the vibrations of pendulum D?
- Give reason for your observation in part (a).
- What type of vibrations take place in pendulums Band C?
- Give reason for the answer in part (c).
Solution
-
The lengths of A and D are equal. When A and D's inherent frequencies are equivalent, D enters a resonance condition. In perfect phase with pendulum A, pendulum D swings at a rate of A.
- This is because the lengths of A and D are equal.
- Forced vibrations have taken hold of B and C.
-
Since the elastic string XY transfers the vibrations from pendulum A to pendulums B and C, the amplitude of their vibrations is similarly tiny.
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