Question

What is the force required for a steel wire to double it's length when it's area of cross section is one square cm. and Young's modules is 200Gpa.

Answer 1

Solution.

$S=1cm^2=10^{-4}m^2;$

$E=200\sdot 10^9 Pa;$

$\Delta l=l_0;$

$F=k\Delta l;$

$k=E\sdot\dfrac{S}{l_0};$

$F=E\dfrac{S}{l_o}\sdot \Delta l=ES;$

$F=200\sdot 10^9\sdot 10^{-4}=200\sdot 10^5 N;$

Answer: $2\sdot10^7 N.$