Moon revolves around the earth due to gravitational force $(F)$ of earth on moon. The work done by the gravitational force is ($r=$ radius of the circular orbit of moon)
(a) $F.2\pi r$
(b) $F.\pi r$
(c) zero
(d) negative work

As known, work done $W=F\times d\times cos\theta$

Here, $W\rightarrow$work done

$F\rightarrow$Force

$d\rightarrow$displacement

$\theta\rightarrow$ angle between the direction of acting force and the direction of the displacement

When the moon revolves around the earth it's a circular motion. And in a circular motion, the direction of the motion is always tangent to the circular path.

Therefore, $\theta=90^{o}$

Therefore, work done $W=F\times d\times cos90^o$

$=F\times  d\times 0$    [$\because cos90^{o}=0$]

$=0$

Therefore, the work done by the gravitational force when the moon revolves around the earth is zero.

Therefore, option (c) is correct.

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Updated on: 10-Oct-2022

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