question_answer

If the stream function is given by \[\psi =3xy,\] then the velocity at a point (2, 3) will be:

A) 7.21 unit                       

B) 10.82 unit

C) 18 unit             

D) 54 unit

Correct Answer: B

Solution :

\[\psi =3xy\] \[u=\frac{\delta \psi }{\delta y}=3x,\] \[v-\frac{\delta \psi }{\partial }=-\,3y\] Resultant velocity, \[v=\sqrt{{{u}^{2}}+{{v}^{2}}}=\sqrt{9{{x}^{2}}+9{{y}^{2}}}\]