Question

What is a unit? How many systems are there for units?

Answer 1

Unit : "Unit is a standard quantity of the same kind with which a physical quantity is compared for its measurement." In the process to know or express the magnitude of a physical qunatity 'Q terms of :

(i) Size of unit (u) used.

(ii) The numerical value of the unit. So, Q = nu

If the size of the unit is changed then the value of n will also change for the same amount of physical quantity Question, Therefore.

$Q=n_1{u}_1=n_2{u}_2=n_3{u}_3.....$

$\Rightarrow nu=Constant$

1. C.G.S. System: It is a French system of units. In this system, length is measured in centimeters (cm), mass is measured in grams (g) and time is measured in seconds (s).

2. M.K.S. System: It is also a French system of units. In this system, length is measured in meters (m), mass in kilograms (kg) and time in seconds (s).

3. F.P.S. System: It is a British system of units. In this system the length is measured is foot (I), mass in pounds (p) and time in seconds (s).