Question

A cylindrical specimen of cold-worked copper has a ductility (%el) of 25%. If its cold-worked radius is 10 mm (0.40 in), what was its radius before deformation?

Option 1: 7.5 mm
Option 2: 12.5 mm
Option 3: 15 mm
Option 4: 20 mm

Answer 1

The original radius of the cold-worked copper specimen was 7.5 mm.

Step-by-step explanation:

To calculate the original radius of the cold-worked copper specimen, we can use the formula for ductility (%el): %el = (r - r0) / r x 100, where r is the final radius and r0 is the original radius. Let's plug in the given values.

25% = (10 mm - r0) / 10 mm x 100

Solving for r0, we have: r0 = (1 - %el / 100) x r = (1 - 25/100) x 10 mm = 0.75 x 10 mm = 7.5 mm

Therefore, the original radius of the copper specimen was 7.5 mm.