Calculate Reynolds number for water at 20 C with velocity 2.0 m/s in a pipe of diameter 0.15 m, using ν = 1.0×10^-6 m^2/s.

• A. 1.50×10^5
• B. 3.00×10^5
• C. 6.00×10^5
• D. 1.50×10^6

Answer: (B)

Reynolds number compares inertial to viscous forces and is found from Re = V D / ν. With V = 2.0 m/s, D = 0.15 m, and ν = 1.0×10^-6 m^2/s, Re = (2.0 × 0.15) / (1.0×10^-6) = 0.30 / 1.0×10^-6 = 3.0×10^5. This is a large, dimensionless number, indicating turbulent flow rather than laminar. The computed value is 3.0×10^5.