Problem $1.(20$ pts$.)$

a $-$ A $2$ m long specimen with a $5$ mm diameter is subjected to a $1500$ N load and is Shown fo deform elastically by $1$ mm $.$ Calculate the diameter of the specimen if it is subjected to a $7000N$ load in tension. Assume ${}_y=300$MPa,$TS=450$MPa and

$u=0\mathrm{.}31.(6$ pts$.($:$)$