This is the chapter One of the first year book. which is called Measurements, deals with the physical quantities and their measurements.

In our physical world, most basic quantities are length,mass and time. Also there are quantities,which can be described in base quantities,called derived quantities.

International System (SI) of Units is a internationally adopted system of units.It consists of seven base units,two supplementary units and several derived units.

Errors may occur while taking any measurement.There are two types of error.An error due to unknown cause is random error and the error due to measuring instrument is called systematic error.

The reasonably reliable digits are called significant figures.

The extent to which systematic error make a measured value differ from its true value is called accuracy of a measurement.
Dimension is the qualitative nature of the physical quantity.Dimension of each base quantity is denoted by a specific symbol written within square brackets.Other physical quantities (such as derived quantities) also have dimensions which are combination of basic ones.