Laws of Motion

Question : 12

Total: 40

A bob of mass 0.1 kg hung from the ceiling of a room by a string 2 m long is set into oscillation. The speed of the bob at its mean position is 1 m s‌–1. What is the trajectory of the bob if the string is cut when the bob is (a) at one of its extreme positions, (b) at its mean position.

Solution:

(a) At each extreme position, the instantaneous velocity of the bob is zero. If the string is cut at the extreme position, the bob is under the action of ‘g’ only, hence the bob will fall vertically downwards.
(b) When the bob is at the mean position, it is affected by gravity. At mean position the bob is having a velocity of 1 m s‌–1 along the tangent to the arc which is in the horizontal direction. If the string is cut at the mean position, the bob will behave as a horizontal projectile. Hence it will follow a parabolic path.

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