Question

A boy has a bag of sand of mass 20kg. first of all, he keeps the bag on his head and move
10 metre. Second time, he drags the bag through 10 metre on a frictionless surface. In
which case, he does more work.​

Answer 1

Explanation:

The boy is moving making an angle of 90 degrees with the directon of application of gravitational force(Force of gravity acts in the downward directon)

So, total work done by man: -

F × S cos ¢(theta)

20 × 10 cos 90

As cos 90= 0

So, F×S cos ¢=0

Hence total work done by man is ZERO.

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Answer 2

Answer:

Explanation: The time when he is dragging it bcz while carrying it on head , the work done would be zero
Hope this will satisfy u

w=f.s

work done by friction = Un (mgcostheta)