Fundamental Units (Cambridge International AS Mathematics)

Fundamental units

What are fundamental units?

• 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 Convert the following into S.I. units:

a) 27.8 km

b) 3.8 hours

c) 0.054 g

Answer:

Exam Hint

• 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 Units e.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).