What is the slope of the graph of stress $\to$ strain up to the elastic limit?

The breaking stress for a wire of radius $r$ of a given material is $F \ Nm^{-2}$. The breaking stress for a wire of the same material of radius $2r$ will be:

What is a plastic body and plasticity?

Match the details of Column-$II$ with the given information in Column-$I$ appropriately.

Column-$I$	Column-$II$
$(a)$ Stress is proportional to strain.	$(i)$ Elastic limit
$(b)$ When the load on the wire is removed, the body regains its original dimension.	$(ii)$ Limit of proportionality
	$(iii)$ Plastic deformation

Wires $W_{1}$ and $W_{2}$ are made of the same material having a breaking stress of $1.25 \times 10^{9} \, N/m^{2}$. $W_{1}$ and $W_{2}$ have cross-sectional areas of $8 \times 10^{-7} \, m^{2}$ and $4 \times 10^{-7} \, m^{2}$,respectively. Masses of $20 \, kg$ and $10 \, kg$ hang from them as shown in the figure. The maximum mass $m$ that can be placed in the pan without breaking the wires is $..... \, kg$. (Use $g = 10 \, m/s^{2}$)

When a load of $80 \,N$ is suspended from a string,its length is $101 \,mm$. If a load of $100 \,N$ is suspended,its length is $102 \,mm$. If a load of $160 \,N$ is suspended from it,then the length of the string is (Assume the area of cross-section is unchanged). (in $\,cm$)