Question

why in carrying so many boxes on head the work done is zero?​

Answer 1

Answer:

Gravitational force on the box is acting in the downward direction. Since the boy walks horizontally, his vertical displacement is zero. Hence, when a boy carrying load on his head moves over a horizontal road, work done against gravitational force is zero.

Answer 2

Answer:

Gravitational force is also acting from opposite direction

so the forces will subtract