Question

10. Look at the activities listed below.Say whether work is done or not.
a. Foodgrains is moving are getting dried in the sun.
b. An engine is pulling a train
c. A sailboat is moving due to wind energy.
d. A boy is walking.
e. A person is carrying a load on his back

Answer 1

Dear student,

Work is done whenever the given two conditions are satisfied:

(i) A force acts on the body.

( ii) There is a displacement of the body by the application of force in or opposite to the direction of force.

a. Food grains do not move in the presence of solar energy. Hence, the work done is zero during the process of food grains getting dried in the Sun.
b. An engine applies force to pull the train. This allows the train to move in the direction of force. Therefore, there is a displacement in the train in the same direction. Hence, work is done by the engine on the train.
c. Wind energy applies a force on the sailboat to push it in the forward direction. Therefore, there is a displacement in the boat in the direction of force. Hence, work is done by wind on the boat.
d. If a boy is walking with a uniform speed hence no work is done
e. While carrying a load, the boy has to apply a force in the upward direction. But, displacement of the load is in the forward direction. Since, displacement is perpendicular to force, the work done is zero.

Regards