A bob of heavy mass is suspended by a light string of length . The bob is given a horizontal velocity as shown in the figure. If the string gets slack at some point P making an angle from the horizontal, the ratio of the speed of the bob at point P to its initial speed is:
Solution
Let the string go slack at P, where the radius makes angle above the horizontal, so P is at height above the lowest point. Slack means tension is zero: , i.e. . Energy: . Hence .
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