Question

No work is done when an object moves

• A. along the direction of force
• B. opposite to the direction of force
• C. at any angle to the direction of force
• D. at 90° to the direction of force

Answer 1

The correct option is D

at 90° to the direction of force

Explanation for the correct option

D: at 90° to the direction of force

Work done is defined as the product of force and distance moved in the direction of the force.

W = Force x displacement x angle between force and displacement

W = F x s x cos ∅

When ∅ = 90° , cos 90° = 0

W = F x s x 0

W = 0

Explanation for the incorrect options

A: along the direction of force

If ∅ = 0° , cos ∅ = 1 and W > 0
B: opposite to the direction of force

If ∅ = 180° , cos ∅ = -1 and W < 0
C: at any angle to the direction of force

If 0° < ∅ < 180°, but ∅ ≠ 90° then W ≠ 0

Hence, no work is done when an object moves at 90° to the direction of the force.