Question

Which of the following quantities have unit as Newton-metre (N-m)?

(A) Work

(B) Energy

(C) Torque

(D) Power

(E) Momentum

Choose the correct answer from the options given below:

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

Hint:

Think about which of these are scalar quantities that share the same unit as work, and which ones bring in time or velocity instead.

Answer 1

The Correct Option is B

Step 1: Newton-metre (N.m) is the unit of any quantity that comes from a force multiplied by a distance.

Step 2: Work is force times displacement in the direction of the force, so its unit is N.m, also called a joule.

Step 3: Energy is the capacity to do work, so it carries the same unit as work, N.m (joule).

Step 4: Torque is the turning effect of a force, found as force times the perpendicular distance from the axis of rotation. Its unit is also N.m, though it is written separately from joule since torque is a vector quantity while work and energy are scalars.

Step 5: Power is the rate of doing work, so its unit is N.m per second, which is the watt, not plain N.m. So option (D) does not qualify.

Step 6: Momentum is mass times velocity, with unit kg.m/s, which has nothing to do with N.m. So option (E) does not qualify.

So Work, Energy and Torque, that is (A), (B) and (C), all carry the unit N.m, matching option 2.