Practicing Success

Target Exam

CUET

Subject

Physics

Chapter

Units and Measurements

Question:

If energy (E), velocity [v] and time (T) are chosen as the fundamental quantities, the dimensional formula of surface tension will be

Options:

[E$v^{−2}T^{−1}$]

[E$v^{−1}T^{−2}$]

[E$v^{−2}T^{−2}$]

[$E^{−2}v^{−1}T^{−3}$]

Correct Answer:

[E$v^{−2}T^{−2}$]

Explanation:
We know that
Surface tension (S)=$\frac{Force[F]}{Lenght[L]}$
So,       [S] = $\frac{[MLT^{-2}]}{L}$
Energy (E) = Force *displacement 
        [E] = [M$LT^{-2}$][L]} = [M$L^{2}T^{-2}$]
Velocity [V] = [L$T^{-1}$]
        
Since S ∝ $E^av^bT^c$
where, a, b, c are constants.
From the principle of homogeneity,
              Dimension of  [LHS] = Dimension of [RHS]
                   $[ML^0T^{-2}]$ =  $[ML^{2}T^{-2}]^a[LT^{-1}]^b [T]^c$
        =[$M^aL^{2a+b}T^{-2a-b+c}$]
Equating the power on both sides, we get

                          a=1 , 2a+b=0 ⇒ b=-2  

                          -2a-b+c= -2 ⇒ c = -2

    So [S] = [E$V^{-2}T^{-2}$]