Question

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: (1) B and D only (2), B and E only (3) A and C only (4) B, D and E only

• A. B and D only
• B. B and E only
• C. A and C only
• D. B, D and E only

Answer 1

Answer: (B)

(2) B and E only

Answer 2

Statement (A) is incorrect: Work done by the man is positive as force and displacement are in the same direction. Statement (B) is correct: Work done by gravity is negative as gravity acts downwards and displacement is upwards. Statement (C) is incorrect: Work done by friction is negative as friction opposes motion. Statement (D) is incorrect: For uniform velocity, applied force equals friction. Work done by applied force is positive. Net work done is zero. Statement (E) is correct: Air resistance always opposes motion, so work done is negative.