NTA Abhyas JEE Main2020PhysicsUnits and DimensionsPractice
If velocity, force and time are taken as the fundamental quantities, then using dimensional analysis choose the correct dimensional formula for mass among the following. [ K is a dimensionless constant ]
Options
- AQ = K v − 1 F T
- BQ = K v 3 F T 2
- CQ = 2 K v − 1 F T
- DQ = 3 K v 2 F T
Correct answer
A. Q = K v − 1 F T
Step-by-step solution
Let the quantity be Q, then, Q = f ( v , F , T ) Assuming that the function is the product of power functions of v , F and T , Q = K v x F y T z . . . ( i ) where K is a dimensionless constant of proportionality. The above equation dimensionally becomes [ Q ] = [ L T - 1 ] x [ M L T - 2 ] y [ T ] z i.e., [ Q ] = [ M y L ( x + y ) T ( - x - 2 y + z ) ] , Now Q = mass i.e., [ Q ] = [ M ] So Equation (ii) becomes [ M ] = [ M y L ( x + y ) T ( - x - 2 y + z ) ] its dimensional correctness requires y = 1 , x + y = 0 an