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 done when Force is done, Displacement takes place and the angle between the force and displacement is not $90^\circ $

Step by step solution
(A) Suma is swimming in a pond.
When she swim’s. She apply force in forward direction and move in forward direction since displacement and force are in same direction Hence work is done
(B) A donkey is carrying a load on its back.
When a donkey is carrying a load on its back. It applying force in upward direction and it is moving in forward direction hence angle between the force and displacement is $90^\circ $so no work is done
(C) A wind mill is lifting water from a well.
 Here it is applying a force in the upward direction and it is moving water in the upward direction since the displacement and force is in same direction so work is done
(D) A green plant is carrying out photosynthesis.
Here no force is involved and the plant does not move since there is no force and displacement Hence no work is done
(E) An engine is pulling a train.
Here engine is applying force in forward direction and it is moving in forward direction since displacement and force is in same direction hence work is done
(F) Food grains are getting dried in the sun.
Here no force is involved and grain does not move hence no work is done
(G) A sailboat is moving due to wind energy.
Here force is applied by the boat in the forward direction and it moving in forward direction since displacement and force is in same direction work is done

Note: Force is an external agent capable of changing the state of rest or motion of a particular body. It has a magnitude and a direction.
Displacement is defined as the act of moving someone or something from one position to another or the measurement of the volume replaced by something else.