Fundamentals of units (SI system) What is the SI unit of power used in physics and engineering measurements?

Introduction / Context:
Power quantifies the rate at which work is done or energy is converted per unit time. This question checks your recall of the correct SI (International System of Units) unit for power used in science and engineering.

Given Data / Assumptions:

• No numerical data are needed.
• Use standard SI base and derived units.
• Work is measured in joules; time is measured in seconds.

Concept / Approach:
By definition, power P = work / time. In SI, work (or energy) is the joule (J) and time is the second (s). Therefore, the SI derived unit of power is joule per second, which has the special name watt (W).

Step-by-Step Solution:

Verification / Alternative check:
Electrical power also uses watts via P = V * I, where V (volt) * I (ampere) yields joule per second, confirming consistency across mechanical and electrical domains.

Why Other Options Are Wrong:

• horsepower: a non-SI unit (1 hp ≈ 746 W).
• joule: unit of energy, not power.
• kg·m: incomplete and not a power unit (and lacks per-second term).

Common Pitfalls:
Confusing energy (joules) with power (watts). Power always involves “per unit time”.

Final Answer:
watt