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
Explanation Suma is doing work as she is pushing water with a certain force in the backward direction to move it some distance and is getting opposite thrust forward. The donkey is exerting force in the upward direction which is perpendicular to the direction of displacement of load and the value of theta thus becomes 90 making the value of work become zero. Therefore, no work is done. Some force is applied against gravity to the water being lifted, both of which are in upward direction hence work is being done. The leaves have no kind of motion in the process of photosynthesis and no force being applied to them either thus there would be no work. The engine is pulling the wagons of train in forward direction by applying force which is again in forward direction hence work is being done As food grains have no kind of motion in the process of drying and no force being applied to them either thus there would be no work. Wind applies force to the sail boat along which the boat has motion in same direction hence work is being done by wind here.
