Question

Examples of zero work for 9

Answer 1

If a very heavy body say, a massive walk is pushed the wall does not move , so no work is done

Answer 2

Work is zero when angle between force and displacement is 90°
We have studied that
Work is donebwhen a force displaces a body in its own direction means angle between force and displacement is 0° .
But if angle is 90° then we know that
W=F.d
W=Fdcostheta
If we add theta as 90° then we know that cos 90°=0 (cos theta is on horizontal axis while 90° means vertical so cos90°=0
W=Fdcos(90)
cos90°=0
W=Fd(0)
W=0
So if angle between F and d is 90° then work done is zero .
And another case where work done is zero is in circular path .
We know that in circle initial point is same as final point so this means that displacement is zero .
Then work done will also be zero