Materials and their use in structures

[alexparker]

A cable has an unstretched length of 12.0m and is stretched by 1.2 x 10^(-4)m when a 6.4 x 10^(8) Pa stress is applied. What is the strain per unit volume in the cable in J m^(-3), when this stress is applied?

Any help would be very nice. I don't understand what to do.

 

[rock.freak667]

When a graph of stress vs. strain is drawn, up to the yield point (or around there), it is a straight line in the elastic region.

It forms a triangle. So the area under that graph gives the energy.