Flow past a rotating cylinder can be simulated by superposition of a doublet, a uniform flow and a vortex. The

peripheral velocity of the rotating cylinder alone is given by $v_{}$ at $r=R(R$ is the radius of the cylinder$).$

A cylinder rotates around its own axis which is perpendicular to the uniform air stream $($density $1\mathrm{.}24k\frac{g}{m^3})$

having a velocity of $11\frac{m}{s}.$ The cylinder is $3m$ in diameter. Find out the speed of rotation of the cylinder

which yields only a single stagnation point on the cylinder.

$N=$