Topic: Fluid Mechanics
Calculate the dynamic head $(P_{A}-P_{static})$ when a jet of water with a velocity, v strikes a flat plate moving with a velocity, u in the same direction as jet. (Take $u=4~m/s,$ $v=10~m/s$ and $\rho=1000~kg/m^{3})$
- A. 8000 Pa
- B. 50000 Pa
- C. 18000 Pa
- D. 98000 Pa
Answer: C. 18000 Pa
Explanation: At the stagnation point, the relative velocity of the jet with respect to the moving plate is $V_{0}=V-u = 10-4 = 6~m/s$. The dynamic head is given by $(P_{A}-P_{static}) = \rho\left[\frac{(V-u)^{2}}{2}\right] = 1000 \times \frac{(6)^{2}}{2} = 1000 \times \frac{36}{2} = 18000~Pa$.