Fundamental quantities and derived quantities

[Manish_529]

Homework Statement

If there are only 7 fundamental quantities then how come we can choose the fundamental quantities according to our will like if we take time and speed as fundamental quantities then length is a derived quantity but it's one of the 7 physical quantity so is this stuff working?

Relevant Equations

The seven fundamental physical quantities are length, mass, time, electric current, temperature, amount of substance and intensity of light

L=Velocity x time here length is directly proportional to time so come is it independent as it should be since it's a fundamental physical quantity

 

[Orodruin]

It is just a matter of convention. You can choose to work in units where there is only a single fundamental physical dimension. It depends on how you define your system of units.

 

[Manish_529]

then the 7 fundamental physical quantities that we read are they incorrect ?

 

[Orodruin]

No. There is no correct/incorrect here. Just definitions.

 

[Manish_529]

No. There is no correct/incorrect here. Just definitions.

so they have been chosen according to what conventions

 

[Orodruin]

so they have been chosen according to what conventions

Choosing them is the convention.