Q120 / 180 · AIIMS 2003 · Physics

Assertion : The amplitude of an oscillating pendulum decreases gradually with time. Reason : The frequency of the pendulum decreases with time.

  • A
    if both assertion and reason are true and the reason is the correct explanation of the assertion
  • B
    if both assertion and reason are true and the reason is not the correct explanation of the assertion
  • Correct answer
    C
    if assertion is true but reason is false
  • D
    if both assertion and reason are false statements.

Solution

The amplitude of an oscillating pendulum decreases with time because of friction due to air. Frequency of simple pendulum is given by $$ f=\frac{1}{2 \pi} \sqrt{\frac{g}{l}} $$ which is independent of amplitude and so even though the frequency remains the same, the amplitude keeps on decreasing till it becomes zero.

Hence, the correct answer is option: 'C'.

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