A 2 kg stone at the end of a string 1 m

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A $2\, kg$ stone at the end of a string $1 \,m$ long is whirled in a vertical circle at a constant speed. The speed of the stone is $4 \,m/sec$. The tension in the string will be $52\, N$, when the stone is

A

At the top of the circle

B

At the bottom of the circle

C

Halfway down

D

None of the above

A $2\, kg$ stone at the end of a string $1 \,m$ long is whirled in a vertical circle at a constant speed. The speed of the stone is $4 \,m/sec$. The tension in the string will be $52\, N$, when the stone is

$mg = 20N$ and $\frac{{m{v^2}}}{r} = \frac{{2 \times {{(4)}^2}}}{1} = 32N$

It is clear that $52 \,N$ tension will be at the bottom of the circle. Because we know that

${T_{{\rm{Bottom}}}} = mg + \frac{{m{v^2}}}{r}$