A structural steel rod has a radius of 10 mm and a length of 1.0 m. A 100 kN force stretches it along its length. The stress produced and the elongation in the rod, respectively, are?

(Young’s modulus of structural steel is $2.0\times {10}^{11} {\mathrm{Nm}}^{-2}.$)

1.   $3.18\times {10}^7 {\mathrm{Nm}}^{-2} \& 2.59 \mathrm{mm}$

2.   $3.18\times {10}^8 {\mathrm{Nm}}^{-2} \& 1.59 \mathrm{m}$

3.   $3.18\times {10}^8 {\mathrm{Nm}}^{-2} \& 1.59 \mathrm{mm}$

4.   $3.18\times {10}^7 {\mathrm{Nm}}^{-2} \& 2.59 \mathrm{m}$

A copper wire of length 2.2 m and a steel wire of length 1.6 m, both of diameter 3.0 mm, are connected end to end. When stretched by a load, the net elongation is found to be 0.70 mm. The load applied is:

Y_C  = 1.1 × 10¹¹ N m² and Y_S = 2.0 × 10¹¹ N m^-2
1.   $1.8\times {10}^2 \mathrm{N}$

2.   $1.8 \mathrm{N}$

3.   $1.8\times {10}^3 \mathrm{N}$

4.   $18\times {10}^3 \mathrm{N}$