Question 17 of 183
Identify the correct statements from the following:
(A) Work done by a man in lifting a bucket out of a well by means of a rope tied to the bucket is negative
(B) Work done by gravitational force in lifting a bucket out of a well by a rope tied to the bucket is negative
(C) Work done by friction on a body sliding down an inclined plane is positive
(D) Work done by an applied force on a body moving on a rough horizontal plane with uniform velocity is zero
(E) Work done by the air resistance on an oscillating pendulum is negative
Choose the correct answer from the options given below:
Show answer and solution
Answer: (A) B and E only
Work done is given by, , where is the angle between the force and the displacement.
case(A): Direction of force and displacement both are in the same direction and hence work done will be positive. Hence, wrong.
case(B): Direction of force and displacement both are in the opposite direction and hence work done will be negative. Hence, correct.
case(C): Direction of force and displacement both are in the opposite direction and hence work done will be negative. Hence, wrong.
case(D): Direction of force and displacement both are in the same direction and hence work done will be positive. Hence, wrong.
case(E): Direction of force and displacement both are in the opposite direction and hence work done will be negative. Hence, correct.
case(A): Direction of force and displacement both are in the same direction and hence work done will be positive. Hence, wrong.
case(B): Direction of force and displacement both are in the opposite direction and hence work done will be negative. Hence, correct.
case(C): Direction of force and displacement both are in the opposite direction and hence work done will be negative. Hence, wrong.
case(D): Direction of force and displacement both are in the same direction and hence work done will be positive. Hence, wrong.
case(E): Direction of force and displacement both are in the opposite direction and hence work done will be negative. Hence, correct.