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Estimation of common physical quantities

Estimation involves finding a value that is reasonably close to the true value of a physical quantity without any measurement. It is used to check any measured or reported values.

If you know that the mass of an adult is about $$70\text{ kg}$$, you can estimate that the mass of a bag of apples must be less than $$70\text{ kg}$$.

Some values of common physical quantities are as follows:

Physical quantity Value
Average mass of an adult $$70\text{ kg}$$
Room temperature $$300\text{ K}$$
Average height of an adult $$1.7\text{ m}$$
Household microwave power consumption $$900\text{ W}$$
Energy in a teaspoon of sugar $$70\text{ kJ}$$

Instead of giving a precise numerical value, it is often sufficient to estimate the order of magnitude of a quantity. This involves just stating the value of ten raised to the appropriate power.

The diameter of an atomic nucleus is around $$10^{-12}\text{ m}.$$

The sun has a mass of roughly $$10^{30}\text{ kg}.$$