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AIIMS2009PhysicsCenter of Mass, Momentum and Collision

Assertion : The bob of a simple pendulum is a ball full of water, if a fine hole is made in the bottom of the ball, the time period first increases and then decreases. Reason : As water flows out of the bob the weight of bob decreases.

Options

  1. AIf both assertion and reason are true and reason is the correct explanation of assertion
  2. BIf both assertion and reason are true but reason is not the correct explanation of assertion
  3. CIf assertion is true but reason is false
  4. DIf both assertion and reason are false.

Correct answer

B. If both assertion and reason are true but reason is not the correct explanation of assertion

Step-by-step solution

When ball is completely filled with water, the centre of gravity of the pendulum is at the centre of the ball when water starts flowing out, the centre of gravity shifts below, thus increasing the length of pendulum, and increasing time period. When ball is more than half empty the centre of gravity again rises up so length of pendulum decreases and time period also decreases.

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