Fundamental units or S.I. units are the international standardised units used around the world
The three main units you will be using are:
Length measured in metres (m) (also called displacement)
1 km = 1000 m, 1 m = 100 cm, 1 cm = 10 mm
Time measured in seconds (s)
1 hour = 60 minutes, 1 minute = 60 seconds
Mass measured in kilograms (kg)
1 kg = 1000 g, 1 g = 1000 mg
All other quantities can be measured in units derived from S.I. units
Worked Example
Exam Tip
Make sure you fully understand the definitions of all the words in this section so that you can be clear about what your exam question is asking of you.
Make sure you are confident converting between fundamental S.I Unitse.g. 17 minutes and 42 seconds = 1062 seconds
2.4 km = 2400 m
86000 mg = 0.086 kg.
Watch out for exam questions using non S.I. units such as feet and inches or miles per hour.
Remember mass (measured in kg) is not a weight (a force measured in Newtons).