In the International System of Units (SI), which unit is used to measure pressure?

Introduction / Context:
Units and dimensions are basic components of physics. Every physical quantity has a specific SI unit that should be memorised for examinations. This question asks you to recall the SI unit of pressure, a quantity that appears in fluid mechanics, thermodynamics, and everyday contexts such as tyre pressure and atmospheric pressure.

Given Data / Assumptions:
- We are dealing with the SI system of units.- The quantity of interest is pressure.- Four common SI units from different branches of physics are listed as options.

Concept / Approach:
Pressure is defined as force per unit area. In SI units, force is measured in newton and area is measured in square metre. So the derived unit of pressure is newton per square metre, written as N / m^2. This derived unit is given a special name: pascal, abbreviated as Pa. The other units listed belong to other physical quantities, such as magnetic flux (weber) and inductance (henry), and are therefore not appropriate for pressure.

Step-by-Step Solution:
1. Recall the definition of pressure: pressure = force / area.2. In SI, use force in newton and area in square metre, so the unit becomes newton per square metre.3. Remember that the special SI name for newton per square metre is pascal.4. Check the options and identify the unit pascal as the one associated with N / m^2.5. Choose pascal as the correct SI unit of pressure.

Verification / Alternative check:
Common examples reinforce this. Meteorologists report atmospheric pressure in pascals or hectopascals, and engineering calculations of stress and pressure use pascal or multiples such as kilopascal and megapascal. This consistent usage confirms that pascal is indeed the official SI unit for pressure.

Why Other Options Are Wrong:
- Newton: This is the SI unit of force, not pressure.- Weber: This is the SI unit of magnetic flux in electromagnetism.- Henry: This is the SI unit of inductance, also used in electromagnetism.

Common Pitfalls:
Students sometimes confuse newton per square metre with newton and choose newton as the answer. Remember that pressure is a derived quantity depending on both force and area, so its unit cannot be just newton. Practice linking definitions with their derived units to reduce such confusion.

Final Answer:
The SI unit of pressure is the pascal, equal to one newton per square metre.