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

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Originally Posted by Natcharaju

In which case work is done and why?

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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?