(i) the highest point of vertical circle
(ii) midway between highest and lowest point in a vertical circle while moving towards the lowest point.
Doubt by Girisha
Solution :
Explanation :
In horizontal circular motion, a bob moves in a circle on a horizontal plane, such as a stone whirled above your head. Gravity acts downward, but it does not affect the circular motion because a normal reaction or a vertical component of tension balances the weight. Only the horizontal component of tension provides the centripetal force. Since gravity does not speed up or slow down the motion, the bob moves with constant speed, and the tension simply keeps the velocity tangential to the circle.
In vertical circular motion, gravity acts along the plane of motion and therefore changes the bob’s speed. As the bob rises, gravity opposes motion and decreases speed; as it falls, gravity increases speed. However, the direction of motion is still tangential at every point because tension maintains the circular path.
When the string is cut, the bob is no longer constrained and immediately becomes a free projectile. It continues with the instantaneous tangential velocity it had at the moment of cutting, and gravity becomes the only force acting on it.
If the string is cut at the highest point, the velocity is horizontal, so the bob follows a parabolic path. If it is cut at the side point, the velocity is straight downward, so the bob undergoes a vertical fall rather than a parabola.
Final Answer :
(i) If the string is cut at the highest point of the vertical circle, then the bob will follow a parabolic path, which is the result of horizontal tangential velocity and the downward acceleration due to gravity acting on it.
(ii) If the string is cut at the midway between highest and lowest point in a vertical circle while moving towards the lowest point then the bob will follow a vertically downward path because both the vertical tangential velocity and downward acceleration are in the same direction.