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:
Answer: (A) B and E only
- (A) The man pulls upward and the bucket moves up: positive work. False.
- (B) Gravity acts down while the bucket moves up: negative. True.
- (C) Friction opposes the sliding: negative. False.
- (D) The applied force balances friction and acts along the motion: positive. False.
- (E) Air resistance always opposes motion: negative. True.
So B and E only.
Solution by Sreeraj P, M.Sc Physics