Q. 1.     Look at the activities listed below. Reason out whether or not work is done in the light of your understanding of the term ‘work’. 

             • Suma is swimming in a pond.

             • A donkey is carrying a load on its back.

             • A wind-mill is lifting water from a well.

             • A green plant is carrying out photosynthesis.

             • An engine is pulling a train.

             • Food grains are getting dried in the sun.

             • A sailboat is moving due to wind energy

Answers (1)

(i) Work done by Suma is negative as the force and displacement are in opposite direction.

(ii) Work done is zero as the gravity on the load is acting vertically downward whereas its displacement is in horizontal direction.

(iii) Work done is positive as both force and displacement are in upward direction.

(iv) Work done is zero as there is no displacement involved.

(v) Work done is positive as force is acting in the direction of the motion.

(vi) Work done is zero as there is no displacement of the grains.

(vii) Work done by wind force is positive as it supports the motion of the boat. 

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