(For Q.1 to 5): Justify giving proper reasoning whether the work done in the following cases is positive or negative :

10/03/2023 Ajit kumar 24 Views 0 Comments

Q.1. Work done by a man in lifting a bucket out of a well by means of a rope tied to the bucket.

Ans. Work done is positive as the bucket moves in the direction of force applied by the man.

Q.2. Work done by gravitational force in the above case.

Ans. Work done by the gravitational force is negative, as the bucket moves upwards i.e., opposite to the gravitational force.

Q.3. Work done by friction on a body sliding down an inclined plane.

Ans. Work done is negative, as frictional force acts opposite to the direction of motion of the body.

Q.4. Work done by an applied force on a body moving on a rough horizontal plane with uniform velocity.

Ans. Work done is positive because applied force acts along the same direction as the direction of motion of the body.

Q.5. Work done by resistive force of air on a vibrating pendulum in bringing it to rest.

Ans. Work done is negative because the resistive force of air always acts opposite of the direction of motion of the vibrating pendulum.