Answer
$728.29\text{ rev/min}$
Work Step by Step
(a)
Let $v_t$ be the tangentail speed and $n$ be the number of revolution per min.
$$v_t=65~\frac{mi}{hr}\times\frac{5,280~ft}{1~mi}\times\frac{1~hr}{60~min}=5,720~ft/hr$$ $$r=\frac{D}{2}=\frac{2.5}{2}=1.25~ft$$ $$n=\frac{v_t}{2\pi r}=\frac{5,720}{2\pi(1.25)}=728.29~rev/min$$
