Question:medium
A bob is whirled in a horizontal circle by means of a string at an initial speed of 10 rpm. If the tension in the string is quadrupled while keeping the radius constant, the new speed is:
A bob is whirled in a horizontal circle by means of a string at an initial speed of 10 rpm. If the tension in the string is quadrupled while keeping the radius constant, the new speed is:
Updated On: May 2, 2026
- 20 rpm
- 40 rpm
- 5 rpm
- 10 rpm
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The Correct Option is A
Solution and Explanation
The centripetal force is supplied by tension (T), where \( T = mv^2/r \). When r and m are constant, T is directly proportional to \( v^2 \). If \( T_2 \) equals 4\( T_1 \), then \( v_2^2 \) equals 4\( v_1^2 \).
Given \( v_1 = 10 \) rpm, then \( v_2 = \sqrt{4 \times 10^2} = 20 \) rpm.
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