Give reason for the following -
A boy is carrying a box on his head and standing ;is he doing any work? Give reason .
A coolie is moving on a road with a luggage on his head. Does he perform work against the force of gravity? give reasons for your answer.
In which of the following cases is work being done :
(a) A boy pushing a heavy rock
(b) A boy climbing up the stairs
(c) A coolie standing with a box on his head
(d) A girl moving on the road.