A square$-$threaded power screw with single thread is used to raise a load of $13,750lb.$

The screw has a mean diameter of $1$ in $.$ and four threads per inch. The collar mean

diameter is $1\mathrm{.}75$ in $.$ The coefficient of friction is estimated as $0\mathrm{.}1$ for both the thread

and the collar.

$($a$)$ What is the major diameter of the screw?

$($b$)$ Estimate the screw torque required to raise the load.

$($c$)$ If collar friction is eliminated, what minimum value of thread coefficient of

friction is needed to prevent the screw from overhauling?