$19.$ A $5$m long bar is made up of two materials as shown in Figure I. The first $2\mathrm{.}75$m of its length is brass and t$812$mm in cross section and the remaining of its length is of steel of $725$mm in cross section. The bur is teasion under a load W Newton and the total elongation of the bar is $1\mathrm{.}5$mm$.$ Determine;a$)$ the load W in Newtonsb$)$ the work done in elongating the bar in Nm

A $5$ m long bar is made up of two materials as shown in Figure $1.$ The first $2\mathrm{.}75$ m of its length is brass and is

$812m{m}^2$ in cross section and the remaining of its length is of steel of $725m{m}^2$ in cross section. The bar is tenstion

under a load W Newton and the total elongation of the bar is $1\mathrm{.}5$ mm $.$ Determine;

a$)$ the load W in Newtons

b$)$ the work done in elongating the bar in Nm $.$

$($Take $E_{\text{s}\text{t}\text{e}\text{e}\text{t}}=200G\frac{N}{m^2}$ and $($:$E_{\text{b}\text{r}\text{a}\text{s}\text{s}}=85G\frac{N}{m^2}\}$

Fig: $1$