2. In which case work is done and why?
(a) A man pushing a wall
(b) A girl climbing a stair case
(c) A boy swimming in a tank
(d) A man standing at a place and holding a suitcase in hand
(e) A lady cooking food
(f) A porter carrying a load on his head walking along a level road
(g) A porter carrying a load and climbing downstairs

In which case work is done and why?


The basic concept to keep in mind is that work is defined as the distance moved against an opposing force. If there's a force but no movement - then no work is done. Or if there is movement but no force opposing that movement - there is no work done. Only when there is movement directly against a force is work done. So from this - what do you think the answers are to the various example you posted?