Measurement is the comparison of unknown quantities with some known quantities. Every measurement has two parts: a number and a unit. This chapter studies three fundamental physical quantities – length, mass and time – their units, the tools used to measure them and the errors to avoid while measuring.
1. Measurement and the Need for Standard Units
- Measurement is needed in daily life – to find one's height, to draw the border lines of a kabbadi court, to buy potatoes, milk or kerosene, or to know how long it takes to reach school.
- To measure quantities we need measuring tools.
- Common terms related to measurement include weight, kilogram, litres, millilitres, kilometre, length and distance.
- When different people measure the same height using a hand span or a cubit, their measurements differ. Similarly, different measuring units are used in different countries.
- All physical quantities have standard units for the sake of uniformity.