A body of mass m is moving in a circle of radius r with a constant speed u . force on body is mv^2/r

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5.Work, Energy, Power and Collision

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A body of mass $m$ is moving in a circle of radius $r$ with a constant speed $u$. The force on the body is $mv^2/r$ and is directed towards the centre. What is the work done by this force in moving the body over half the circumference of the circle?

A

$\frac {mv^2}{r}\,\times \pi r$

B

zero

C

$\frac {mv^2}{r}$

D

$\frac {\pi r^2}{mv^2}$

Solution

Work done by centripetal force is alwase zero because force and instantaneous displacement are always perpendicular

$W=\vec{F}-\vec{S}=F s \cos \theta s \cos \left(90^{\circ}\right)=0$

Standard 11

Physics

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