Problem $2(20$ Points$)$

A single$-$threaded acme power screw is used to raise a load F $.$ The screw has a root diameter of $1\mathrm{.}5$ in $.$

and four threads per inch. The collar mean diameter is $2\mathrm{.}25$ in $.$ The coefficient of friction of threads

and collar is estimated as $0\mathrm{.}12$ and $0\mathrm{.}08,$ respectively. Determine the force F if the required power to

raise the load is $1\mathrm{.}3$ hp at a speed of $20$rev$//$min$.$

Answer is F $=19$ kips. How?