Question

what is unit explain the importance of unit in the measurement what do you mean by the fundamental and derived unit

Answer 1

A unit of measurement is a definite magnitude of a quantity, defined and adopted by convention or by law, that is used as a standard for measurement of the same kind of quantity.
Importance of unit are given below----
1. Many of measurement are easier to calculate and use with.
2. Better accuracy for what is being measured.
3. Magnitude more understandable.

Fundamental unit are units which are used to measure the fundamental quantities are called fundamental unit. eg- metre, kilograms, ampere etc.
The units which are derived from fundamental unit are called derived units. eg- cubic metres, kilograms/cubic metres etc.

Answer 2

The standard to measure a physical quantity is called a unit of that quantity. To compare two objects of the same quantity and determine which one is more and which one is less, units are used.

Explanation:

• To measure a physical quantity, a standard is needed. This standard for measuring physical quantities is called unit
• For example, if we have some rods, then how do we measure their length?
• We take one rod and assume its length is one unit and measure other rods by comparing them with the unit length rod.
• If the 2nd rod is three times to unit length rod, we say, its length is three units. Similarly for the other rods.
• In the same way, kg is the unit of mass, second is the unit of time, meter is the unit of length, meter per second is the unit of velocity and Newton is the unit of force etc.

• Now assume that we have two stones, how do we decide which one is heavy and which one is light? For this, we use unit kg.
• Say one stone is 5 kg and the other is 5.5 kg, then, we can easily say that the second stone is heavy. Therefore, to measure the quantities the units are very important.
• There are seven base quantities mass, length, time, amount of substance, temperature, electric current and luminous intensity.
• Corresponding to these quantities, the units are kilogram, meter, second, mole, kelvin, ampere and candela respectively. These are called fundamental units.
• All other units which are derived by these units are called derived units, for example, $m/s$, Newton ($N$) etc.

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