9702 · 1.1
Physical quantities
Physical quantities are how we describe the world around us, always needing a number and a unit. We use special units, understand directions, and account for tiny errors in our measurements.
Need to know
What you need to know
- 1.1 Physical quantities.
- Physical quantities consist of a numerical magnitude and a unit.
- Eg. When you are driving, the speedometer shows the speed as 120 km/h. The physical unit here is speed, with 120 being the numerical magnitude and km/h being the unit.
Explanation
Measuring the Universe: Your Physics Toolkit
- Identify the type of quantity: Is it a **scalar** (magnitude only) or a **vector** (magnitude and direction)?
- Master the SI units: Learn base units, understand derived units, and use **prefixes** for scale.
- Check equation validity: Ensure units match on both sides of an equation (this is **dimensional homogeneity**).
- Minimise measurement errors: Understand **accuracy**, **precision**, and how to reduce **random** and **systematic errors**.