The derived unit of pressure can be expressed as

Analyze the question: We need to express pressure in terms of base SI units (kg, m, s).

Concept: Pressure is force per unit area.

P = F / A

Force from Newton's second law: F = ma, so the unit of force is kg·m·s⁻² (the newton).

Area has the unit m².

Solution:

Unit of pressure = (kg·m·s⁻²) / m²

= kg·m^(1−2)·s⁻²

= kg·m⁻¹·s⁻²

This is the pascal (Pa): 1 Pa = 1 N/m² = 1 kg·m⁻¹·s⁻².

Checking the options:

• A. kg·m·s⁻² is the unit of force (newton), not pressure.
• B. kg·m⁻¹·s⁻² matches our result.
• C. kg·m⁻²·s⁻² has the wrong power of m. It would come from dividing force by m³.
• D. kg·m⁻¹·s² has the wrong sign on the power of s.

Tip: For derived units, build from the definition. Force = kg·m·s⁻², then divide by the area (m²) for pressure. The mass stays in the numerator, and the powers of m subtract (1 − 2 = −1). Also, a quick check: any option equal to the newton (kg·m·s⁻²) is a force, so you can eliminate it right away.