Estimation
Physics: AQA A Level, topic 1.1.9
Order of Magnitude
The order of magnitude of a number is the power of 10 that most closely approximates it. It refers to the scale (or size) of a value. Each power of 10 represents a different order of magnitude.
Height of a human
- The height of an average adult in the UK is about 1.70 m.
- The order of magnitude estimate for the height of a human is 1 m.
- 1 m is more appropriate than 0.1 m or 10 m.
Mass of the Sun
- The actual mass of the Sun is 1.989 ×1030 kg.
- A sensible order of magnitude estimate to use is 1030 kg.
Walking speed
- We can estimate that we walk at a speed of 1 m/s.
- In reality, we might walk slightly faster or slower - but 1 m/s is a better estimate than 0.1 m/s, 10 m/s or 100 m/s!
Test yourself on Estimation
Which of these objects has an order of magnitude estimate of 1 kg?
What order of magnitude should we use for the speed of a car driving steadily along a high street?
What order of magnitude should we use for the height of a house?