Question

A man is dragging a large trunk on the ground by applying a force at an angle ‘θ’ to the horizontal. The work done by i) gravity on the trunk, ii) man on the trunk & iii) frictional force on the trunk will be

• A. Positive, Negative and Zero respectively
• B. Negative, Positive and Zero respectively
• C. Zero, Negative and Positive respectively
• D. Zero, Positive and Negative respectively
• E. Always positive

Answer 1

The correct option is D

Zero, Positive and Negative respectively

i) W_gravity = F_gravity x s x Cost90^o = F_gravity x s x 0 =0J [F_gravity = weight]

ii) W_man = F_man x s x Cosθ

ii) W_friction = F_friction x s x Cos180^o= F_friction x s x (-1) =-F_friction x s