Basics of units in mechanics In engineering mechanics and physics, the SI unit named “joule” is used to measure which physical quantity?

Introduction / Context:
The International System of Units (SI) assigns standard units to physical quantities so engineers and scientists can communicate unambiguously. The “joule” is frequently encountered in mechanics, thermodynamics, and electrical engineering. This question tests whether you can correctly associate the joule with the right physical quantity.

Given Data / Assumptions:

• We use SI units.
• Force is measured in newton (N), work/energy in joule (J), power in watt (W), and velocity in m/s.
• Work is defined as force applied through a distance in the direction of motion.

Concept / Approach:
Work and energy share the same SI unit because work done on a system changes its energy. By definition, 1 joule is the work done when a force of 1 newton acts through a distance of 1 metre: 1 J = 1 N * 1 m. Recognizing this mapping avoids confusing “power,” which measures the rate at which work is done and is expressed in watts (1 W = 1 J/s).

Step-by-Step Solution:
Identify quantity linked to joule.Recall definition: Work W = Force * displacement (in direction of force).Unit analysis: N * m = joule (J).Therefore, “joule” is the unit of work (and energy).

Verification / Alternative check:
Energy forms (potential, kinetic, electrical) are all measured in joules, reinforcing that joule is the energy/work unit. Power being J/s confirms its distinct unit, watt.

Why Other Options Are Wrong:

• Force → newton (N), not joule.
• Power → watt (W), not joule.
• Velocity → metres per second (m/s), not joule.

Common Pitfalls:

• Confusing energy (J) with power (W). Power is a rate; energy/work is an amount.

Final Answer:
work