Question

Which of the following is not an SI unit?
A.Metre
B.Pound
C.Kilogram
D.Second

Answer 1

Hint: There are fundamental physical quantities like length,mass and time. We have two units to measure them namely fundamental units and derived units. Fundamental units are called fundamental because they are not made from other units and cannot be made into simpler units. Examples are units like mass,length etc. Derived units are a combination of fundamental units. Example m/s etc. There are three systems which are M.K.S system, C.G.S system and F.P.S system.

Complete answer:
As I mentioned that there are three systems, let us see what they denote. Firstly, the M.K.S system measures the unit of length in metres, mass in kilograms and time in seconds, hence the name M.K.S. The C.G.S system measures the length in centimetres, mass in grams and time in seconds whereas the F.P.S system measures the length in foot, mass in pounds and time in seconds. There is another system of measurement called the S.I system which is the International System of measurement. The M.K.S system is the fundamental core for the S.I system. It also measures the length,mass and time in terms of metres, kilograms and seconds respectively, but it differs from M.K.S in some of the features. Apart from length,mass and time, the S.I unit also measures other parameters such as electric current, temperature, light intensity and amount of substance. This is about different systems of measurement. All the options mentioned above come under S.I system except pound which comes under F.P.S system.

So, the correct option is B.

Note:
As I said, the S.I system measures the other units, it measures electric current in Amperes, temperature in Kelvin, amount of substance in moles and light intensity in Candela. There are many other units which are derived from S.I units. Some of them are force, momentum, magnetic field etc.