$(1)$ Two copper bars & one alueninilum

bar are held by pins at their ends

The bats ate separated by providong

thin spaces between theen Each

copper has $50mm12\mathrm{.}5mm$ whil m

aluminilun bat is $50nm25mm$

It remperature of assembly is

raised by $40C$ find average sheer

stress produced in $10$ mm diamerer

pons.

letven:

$E_c=1\mathrm{.}2{10}^5\frac{N}{m}{m}^2$

$E_a=0\mathrm{.}7{10}^5\frac{N}{m}{m}^2$

${}_c=1\mathrm{.}6{10}^{-5}$ per $C$

${}_a=2\mathrm{.}2{10}^{-5}$per$C$