Look at the activities listed below. Reason out whether or not work is done in the light of your understanding of the term ‘work’:
(a) Suma is swimming in a pong.
(b) A donkey is carrying load on its back.
(c) A wind-mill is lifting water from a well.
(d) A green plant is carrying out photosynthesis.
(e) An engine is pulling a train.
(f) Food-grains are getting dried in the sun.
(g) A sailboat is moving due to wind energy.
(a) Work is done because the displacement of swimmer takes place in the direction of applied force.
(b) A donkey is not doing work against gravity. No work is done as the displacement of load does not take place in the direction of applied force.
(c) Work is done, as the displacement takes place in the direction of force.
(d) No work is done, because no displacement takes place.
(e) When an engine pulls a train the angle between distance and force becomes 0° and work will be done.
(f) No work is done in this process as the grains are not moving or covering some distance when being dried in the sun, hence no work is done.
(g) When wind energy is applied to the boat it starts moving in the direction of the force applied by the wind. So the angle between distance and force becomes 0° and some work will be done.