The Unit of Work done is Joule. 1 Joule = ______?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → 1 Joule = 1 Newton × 1 Metre
Work done is force × displacement in the direction of the force, \(W=F\times s\). So the unit of work is the unit of force times the unit of length: 1 joule is the work done when a force of 1 newton moves a body through 1 metre in its own direction.
Why the other options are incorrect
Option (2) 1 Joule = 1 Kilogram × 1 Metre — Incorrect. The kilogram is a unit of mass, not force; a joule is 1 kg m2/s2.
Option (3) 1 Joule = 1 Newton × 1 Kilogram — Incorrect. Force times mass gives no standard physical quantity; work needs a distance.
Option (4) 1 Joule = 1 Newton × 1 Second — Incorrect. The newton-second is the unit of impulse (force × time), equal to a change in momentum.