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 windmill 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.

AcademicPhysicsNCERTClass 9

$(a)$. Because the displacement of the swimmer takes place and a force is applied by the swimmer, so the work is done.

$(b)$. Donkey is not doing any work in carrying the load as weight (acting vertically downward) and displacement (acting horizontal) are perpendicular to each other. But, it does work against friction between its hoofs and the ground.

$(c)$. As the displacement of water takes place and a force is applied by the windmill, So the work is done. The windmill does work against gravity.

$(d)$. No work is done because no displacement takes place.

$(e)$ Here, the displacement of the train takes place and a force is applied by the engine, So the work is done because.

$(f)$. No work is done because displacement does not take place.

$(g)$. Work is done as the displacement of the sailboat takes place and a force is applied by the wind.

raja
Updated on 10-Oct-2022 13:22:47

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