A square$-$threaded power screw with single thread is used to raise a load of $25,000lb.$ The screw

has a mean diameter of $1$ in $.$ and four threads per inch. The collar mean diameter is $1\mathrm{.}5$ 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?