A block A, whose weight is 100N, is pulled up a slope of length 5m by means of a constant force F (=100N) as illustrated.

(a) What is the work done by the force F in moving the block A, 5m along the slope?

(b) What is the increase in potential energy of the block A?

(c) Account for the difference in the work done by the force and the increase in potential energy of the block.

Given,

F = 100 N

h = 3m

displacement = 5m

We know,

(i) Work done = Force × displacement in the direction of the force

$W = 100 \times 5 \\[0.5em] \Rightarrow W = 500 J \\[0.5em]$

(ii) The potential energy gained by the block U = mgh

$\text{P.E.} = 100 \times 3 \\[0.5em] \Rightarrow \text { P.E. gained by the block}= 300 J \\[0.5em]$

(iii) The difference (200 J) energy is used in doing work against the force of friction between the block and the slope and it will appear as heat energy.