Question

A student lifts the object in an upwafd direction in doing so he applies the force on the object in the upper direction and displaces it in that direction (however the force of gravity also acting on the object)

1. State the direction in which the force of gravity acting on it which one of these forces doing positive and negative work.Give reason.

Answer 1

Force of gravity always act towards the centre of the earth.
Since direction of motion of object and force due to gravity is in opposite direction therefore work done is negative.
Where as force applied by man and motion of a object is in same direction therefore work done is positive.