What work does the boy do when applying a force of 60 N to lift a 20 N block to a height of 1.5 m?

Given:

F = 60 Newton – the force applied by the boy;

P = 20 Newton – bar weight;

h = 1.5 meters – the height to which the boy lifts the bar.

It is required to determine A (Joule) – the work done by the boy while lifting the bar.

Let’s find the resultant of all the forces acting on the bar:

F1 = F – P = 60 – 20 = 40 Newtons.

Then, the work done by the boy will be equal to:

A = F * h = 40 * 1.5 = 60 Joules.

Answer: when lifting the bar, the boy will do a work equal to 60 Joules.