A `10 kg` block is pulled along a frictionless surface in the form of an arc of a circle of radius `10 m`. The applied force is `200 N`. Find the work done by (a) applied force and (b) gravitational force in displacing through an angle `60^@`.
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Explanation

Work done by applied force `W = Fr sin theta`
`W = 200 xx 10 xx sin 60^@ = 200 xx 10 xx (sqrt(3))/(2) = 1732 J`
work done by gravitational force
`W = -mgr(1 - cos theta)`
`W = -10 xx 9.8 xx 10(1 - cos 60^@)`
`W = -98 xx 10(1 -(1)/(2)) = - 490 J`.