(a) No, work is done because the force acting on the earth and the displacement along the tangent are perpendicular to each other.
Since W = FS cos 0 and = 90°, therefore, cos 90° = 0 Hence, W = 0.
(b) Since coolie is applying force on the heavy box to hold it but there is no displacement of
the box. Therefore, work done by him is zero.
(c) F = (70 + 10) = 80 kg wt = 80 x 10 = 800 N
S = 100 m
W = F x S = 800 x 100 = 80000 J