What prevents the stone from revolving in a horizontal circle of centre A? Explain?
Answers:
To whirl the string around you need the movement of the hand holding the string. The hand itself will be moving in a horizontal circel with the centre of A. No hand circle, no stone circle.
Is that what you were meaning??
It's a vector related question. The plane of the circle, centre O is below the string anchor point A. You have two vector forces. The centrifugal force, pulling the stone out from point A, and gravity, acting straight down. The result of the two vectors gives the angle between the string and horizontal plane. If the centrifugal force is equal to gravity, the angle will be 45 degrees (a slow swing). The faster you whirl the stone, the greater the centrifulgal force, and the less the angle, but the angle will never get to zero as gravity will always have some effect.
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