Help with Part B and C of Assignment

[techick]

I don't have any idea on part b and c.
Anyone would show me how to do them?

 

[Astronuc]

How was the first part answered, and does one see any relevancy to the subsequent questions?

For a two-dimensional incompressible flow in the x,y plane, the conservation of mass (continuity) equation can be written as,

\frac{\partial u}{\partial x}\,+\,\frac{\partial v}{\partial y} = 0

and since the flow is rotational,

\nabla\times\nabla\phi\,\neq\,0

where \phi = velocity potential.