Question

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.

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
• C. Assertion is correct but Reason is incorrect
• D. Both Assertion and Reason are incorrect

Answer 1

Answer: (B)

Both statements are true but the reason is not the correct explanation of the assertion.

When the ball is full of water, the center of gravity of pendulum is at the center of the bob.

When water starts flowing out, the center of gravity of ball shifts down, increasing the length of the pendulum, thus increasing the time period.

When ball is more than half empty, the center of gravity again rises up, decreasing length of pendulum, thus decreasing the time period.