A boy whirls a stone tied to a thread ,such that the stone moves uniformly irt a circle. What must be the length of the thread if the stone completes 42 rounds in a minute with a uniform speed of `2.2 ms^(-1)` ?

Explanation

Here length of the thread forms the radius of the cicular path in which the stone moves.
Given frequency of revolution .
v = 42 rev/minute.
` v = 42/60` rev/s
But speed ` v = ( 2 pi R)/T = 2piRv`
` ot R = v /( 2 pi v) = (2.2)/( 2 xx 22/7 xx 42/60) = 0.5 m`