Question

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 pond.
(B) A donkey is carrying a 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.

Answer 1

Hint
Work is said to be done, when the body or object displace some distance due to applied force. So, work is directly proportional to the product of the force applied and the displacement of the body or object.

Complete step by step answer
Considering the given activities,
(A) We are given that Suma is swimming, So, Suma is pushing the water in the backward direction. Therefore, the force is acting on the body. Hence, work is done.
(B) When the donkey is moving in the upward direction then force exerted by the donkey is perpendicular to the displacement of the load. So, no work is done.
(C) As the windmill is lifting the water from the well against the force of gravity. Therefore, work is said to be done.
(D) The work is said to be zero as the leaves of the plant at rest during the process of photosynthesis. So, no work is done.
(E) The engine is pulling the train. The engine and the train applied the force in the same direction and made a displacement in the same direction. So, the work is said to be done by the engine.
(F) Food grain in presence of sun is dried. There is no displacement and the force. So, no work is done.
(G) As the wind moves the sailboat. There is force applied and there is displacement of the boat. Therefore, work is said to be done.

Note
Force is defined as the push or pull upon an object. Force is directly proportional to the product of the mass of the body and the acceleration due to gravity. The SI unit of the force is Newton.