Question: what is the dimensional formula for critical velocity?
Answer: Dimensional formula of: Coefficient of viscosity (𝜂): M1L-1T. Radius (r) : M0L1T. Density of fluid (⍴): M1L-3T. Critical velocity: V_{c}=\frac{\left [ M^{0}L^{0}T^{0} \right ]\left [ M^{1}L^{-1}T^{-1} \right ]}{\left [ M^{1}L^{-3}T^{0} \right ]\left [ M^{0}L^{1}T^{0} \right ]}