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The diagram below displays four solid plastic balls attached to wires, all mounted on a wooden base. When a person shakes the wooden base back and forth at a steady pace, the balls begin to vibrate as well. It is noted that while all the balls vibrate, only one of them vibrates vigorously.

The diagram below displays four solid plastic balls attached to wires, all mounted on a wooden base. When a person shakes the wooden base back and forth at a steady pace, the balls begin to vibrate as well. It is noted that while all the balls vibrate, only one of them vibrates vigorously. ICSE 2025 Improvement Physics Solved Question Paper.

(a) Explain why only one ball vibrates vigorously.

(b) If fA, fB, fC, and fD are the natural frequencies of vibration of the wires, then arrange them in the increasing order of their frequencies and justify.

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Answer

(a) As the frequency of vibration of the wooden base matches with the natural frequency of only one ball, it starts to vibrate vigorously due to resonance which increases the amplitude of vibration of the ball.

(b) Since frequency of vibration in a wire is inversely proportional to the vibrating length.

Let,

lA, lB, lC and lD are length of the wire A, B, C and D respectively.

From the figure,

lB < lC < lA < lD

Then,

fD < fA < fC < fB

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