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’.
• 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.

Answer 1

Work Done in Different Activities: 

According to physics, work is said to be done when a force is applied on an object and the object is displaced in the direction of the force.

• Suma swimming in a pond: Yes, work is done. She applies force to move through water and is displaced.
• A donkey carrying a load on its back: No, work is not done on the load in the vertical direction because there is no displacement in the direction of the applied force (weight of load is vertical, motion is horizontal).
• A wind-mill lifting water from a well: Yes, work is done. Force is applied to lift water and displacement is upward.
• A green plant carrying out photosynthesis: No, work is not done in the physics sense. Energy is used, but there is no displacement caused by a force.
• An engine pulling a train: Yes, work is done. Force is applied on the train and it is displaced in the direction of the force.
• Food grains drying in the sun: No, work is not done in the physics sense. Heat energy is absorbed but no displacement occurs due to force.
• A sailboat moving due to wind energy: Yes, work is done. Force of wind displaces the boat in the direction of the force.