Which of the following units is equivalent to the watt?

Analyze the question: We need the SI base-unit form of the watt (W), the unit of power.

Concept: Power is the rate of doing work (or energy transfer):

P = Work ÷ Time = Force × distance ÷ time

Solution:

1. Force (newton) = mass × acceleration = kg·m·s⁻²
2. Work (joule) = force × distance = kg·m·s⁻² × m = kg·m²·s⁻²
3. Power (watt) = joule ÷ second = kg·m²·s⁻² ÷ s = kg·m²·s⁻³

Checking the options:

• A. kg·m·s⁻² is the newton (force).
• B. kg·m²·s⁻³ is the watt (power).
• C. kg·m²·s⁻² is the joule (energy or work).
• D. kg·m²·s⁻¹ has the units of angular momentum, not power.

Tip: Work down the chain: newton → joule → watt. Each step adds one factor of m (N to J) or one factor of s⁻¹ (J to W). Starting from kg·m·s⁻², multiply by m to get kg·m²·s⁻², then divide by s to get kg·m²·s⁻³.