Question

A 40kg girl is running along a circular path of radius 1 m with a uniform speed. how much work is done by the girl in completing the circle??

Answer 1

Work done is zero
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As we all know ,
Work done = Force x Displacement.


Here in this case , force is acting , but displacement is not there.
Displacement is the shortest distance from initial position to final position.


W = F x s
If s = 0 , W = 0
When displacement is zero ,
work done is also zero

Answer 2

Mass = 40 g

Force = mass x gravity
          = 40 x 9.8
          = 392 N
          
After a complete rotation, Displacement is zero.

Displacement = 0

Work done = force x displacement
                  
                   = 392 x 0
                    = 0

Hence, no work is done by girl.