Q.1 A coolie carry suitcase on his head and moves on horizontal path. How much work done by him with respect of gravity and why ??
Answers
Answer:
if a coolie walks on level road with load on his head he is moving himself and also he is moving the object.
So to move himself on the level road he is applying force on himself to displace him so here he is doing work which is equal to the product of the force applied and the displacement.
He is moving the load on his head which already on his head so here is applying the force on the body to accelerate it. So the work done by him to move the load is equal to the change in the load’s kinetic energy (here is no change in potential energy as the height of the object is not changed.
Acceleration is in vertically downward but his displacement is only in horizontal direction.
Work done = force (in vertical direction) x displacement (in vertical direction)
Work done = (load + weight of coolie) x 0 = 0
Hence, work done against gravity is zero.