Question

the workdone against gravity by a man carrying a heavy load of 70kg and walking along a level road is

Answer 1

mass of load = 70 kg
as man is walking along a level road so the carrying load is perpendicular to the surface and the force applied by that man.
whenever the angle between the force and the displacement is 90 . then the value of cos¤ becomes 0 .
so, work done = F × cos¤ × S
= 70 × 0 × S
=0
Hence, the work done by man is 0