Study the following three situations and answer the questions given below
PHYSICS · Subjective · A Level · Physics · Mechanics and materials · Mechanics and materials
Problem
Study the following three situations and answer the questions given below.
Situation I : A worker pushes a box along a horizontal floor by applying a force through a handle that is inclined at 40∘ above the horizontal.
Situation II : A crane lowers a concrete block vertically downward while its cable exerts an upward tension making an angle of 180∘ with the displacement of the block.
Situation III : A boy carries his school bag on his shoulder and walks straight along a level road.
(i) For each situation, state whether the work done by the mentioned force is positive, zero or negative.
(ii) For Situation II, explain your answer in part (i) with reference to the angle between the force and the displacement.
(iii) If, in Situation I, the handle were held at 90∘ to the horizontal instead of 40∘, what would be the work done by the worker? Give a reason.