Chapter 2 of 13All chapters
Chapter 2 of 13
Units and measurement
Seven base units and why they matter.
The SI system
Metre, kilogram, second, ampere, kelvin, mole and candela are the base units, and everything else is built from them. A newton is a kilogram metre per second squared.
- Checking that units match on both sides catches most algebra errors.
- A mismatch between metric and imperial units destroyed a Mars orbiter in 1999.
Significant figures
An answer cannot be more precise than the measurements it came from. Quoting ten digits from a ruler reading is a claim you cannot support.