Homework$-$Week $11($show your work$)$

$($P$37)$ Suppose that we hang a heavy ball with a mass of $10$ kg $($about $22$lb$)$ from a steel wire $3$ m long that is $3$ mm in diameter. Steel is very stiff, and Young's modulus for steel is unusually large, $2{10}^{11}\frac{N}{m^2}.$ Calculate the stretch $L$ of the steel wire. This calculation shows why in many cases it is a very good approximation to pretend that the wire doesn't stretch at all $("$ideal nonextensible wire"$).(10$ points$)$

$($P$44)$ A $15$kg box sits on a table. The coefficient of static friction ${}_s$ between table and box is $0\mathrm{.}3,$ and the coefficient of kinetic friction ${}_k$ is $0\mathrm{.}2.($a$)$ What is the force required to start the box moving? $($b$)$ What is the force required to keep it moving at constant speed? $($c$)$ What is the force required to maintain an acceleration of $2\frac{m}{s^2}(15$ points$)$