Question

Negative work can be done (a) by friction on the tires while a car is accelerating without skidding. (b) by a spring at the bottom of an elevator shaft when it stops a falling elevator. (c) by a hand catching a ball. (d) by all of the above. (e) only by (b) and (c) above.

Answer 1

Answer:

(a) by friction on the tires while a car is accelerating without skidding.

Explanation:

Negative Work is done, when the body moves in a direction, that is completely opposite to the direction of the force applied. Thus, the angle between force and displacement becomes 180°, and the Cos 180° in formula gives -1.

(a) Since, the frictional force acts opposite to the direction of motion of the car or tires. Therefore, negative work can be done by friction.

(b) The motion of spring is in the direction of force. Thus, it does not give negative work.

(c) Since, the ball finally stops in handle. Thus this is not the case of negative work.

Therefore, the correct answer is:

(a) by friction on the tires while a car is accelerating without skidding.