If the stream function is given by $\Psi = 3xy$, then the velocity at a point (2, 3) will be
- A. 7.21 unit
- B. 18 unit
- C. 10.82 unit
- D. 54 unit
Answer: C. 10.82 unit
Explanation: $v = \partial\psi/\partial x = 3y$, $u = -\partial\psi/\partial y = -3x$. At (2,3), $v = 9, u = -6$. Resultant = $\sqrt{(-6)^2 + 9^2} = \sqrt{36+81} = \sqrt{117} \approx 10.82$.