Question

The SI unit of length is?
A- metre
B- kilometre
C- Foot
D- Yard

Answer 1

Hint: SI units are called standard units. We have 7 basic quantities in physics. These are length, time, mass, temperature, amount of substance and luminous intensity. Their SI units are called fundamental units and they cannot be derived by using other units of measurement. Length is the unit of measurement and is one dimensional.

Complete answer:
We need to find the SI unit of length and we are given with four options. Let us look at them one by one. All the four units given are used for measurement of length but the SI unit of length is metres. So, the SI unit of length is metre.

So, the correct answer is “Option A”.

Additional Information:
When we say that the unit is a fundamental quantity then we imply we cannot derive that. For example, Watt is not a fundamental unit because it cannot be derived and can be written as Joules/s.

Note:
Foot is used as the standard unit of measurement of length in the United States of America. Foot is given preference to the meter there in commercial and engineering measurements. The foot was used by the Greeks, Romans, Chinese & French. Using metre for measurement of length first started in France early after the great French Revolution in 1700. Also, it is the SI unit of measurement of length and all international measurements which are not so big are measured in terms of metre.