A coolie carries a load of 50kg on his head and walks on a level road up to 100m. what is the work done by him.
The work done would be zero.
Consider the following...
mathematically, work done is written as
W = F.s = FsCosθ
F is the force applied, s is the displacement caused
F = mg = 50 X 10 = 500 N
s = 100 m
and θ is the angle between (vectors) F and s
as F and s are perpendicular, θ = 90o
W = FsCos90 = 0