Look at the activities listed below.
Reason out whether or not work is done in the light of your understanding of the term 'work'.
(i) Suma is swimming in a pond.
(ii) A donkey is carrying a load on its back.
(iii) A windmill is lifting water from a well.
(iv) A green plant is carrying out photosynthesis.
(v) An engine is pulling a train.
(vi) Food grains are getting dried in the sun.
(vii) A sailboat is moving due to wind energy.

Explanation

(i) Yes. Suma is doing work. She pushes water in the backward direction and the displacement is in forward direction.
(ii) No. The work done by donkey is zero. The force exerted by the donkey in the upward direction is perpendicular to the horizontal displacement of the load.
(iii) Yes. The work is done in lifting the water against the force of gravity.
(iv) No. The leaves of plant remain at rest during photosynthesis.
(v) Yes. The force applied by the engine and the displacement of the train are in the same direction.
(vi) No. Here there is no displacement.
(vii) Yes. The work is done by the wind in moving the sailboat.