A venturimeter of 20mm throat diameter is used to measure the velocity of water in a horizontal pipe of 40 mm diameter. If the pressure difference between the pipe and throat sections is found to be 30 kPa, then, neglecting frictional losses, the flow velocity is
- A. 0.2 m/sec
- B. 1.0 m/sec
- C. 1.4 m/sec
- D. 2.0 m/sec
Answer: D. 2.0 m/sec
Explanation: Q = A1 A2 / $\sqrt{A1^2 - A2^2}$ * $\sqrt{2gh}$. Or V2 = $\sqrt{2gh / (1 - (A2/A1}$^2)). h = P/w = 30000/9810 = 3.058m. A2/A1 = (20/40)^2 = 1/4. V2 = $\sqrt{2*9.81*3.058 / (1 - 1/16}$) = $\sqrt{60 / 0.9375}$ = $\sqrt{64}$ = 8 m/s? Wait, question asks flow velocity (in pipe V1). V1 = V2 * (A2/A1) = 8/4 = 2 m/s.