A labourer whose own mass is 50 kg carries a load of an additional 60 kg on his head to the top of a building 15 m high. Find the total work done by him. Also, find the work done by him, if he carries another additional block of mass 10 kg to the same height.

W = mgs cos90° = 110 x 9.8 x 15 cos90°

W =0

If additional block of mass 10 kg is carried by him to the same height, then also work done by him remains zero because force and displacement are perpendicular to each other (i.e. 0 = 90°).