Write down the following equation: Vc = (k*μ)/(d*r). This is the basic formula for calculating critical velocity (Vc). The variable "k" represents the Reynold's number. The variable "μ" represents the coefficient of viscosity of liquid and is measured in meter square per second. The variable "d" and "r" represents the radius of tube and density of liquid respectively. The density of the liquid is measured in kg per meter cube.
Note the value of Reynold's number given in your problem. If the value of Reynolds number lies between 0 to 2,000, the flow of liquid is streamline or laminar. If the value of Reynolds number is greater than 3,000, the flow is turbulent. For values in between, the flow is not steady.
Solve the formula of critical velocity using simple algebra. The resulting value of critical velocity will be in meter per second.