How many coats having the same mass as those in exercise 10 must be hung on the

Question:

How many coats having the same mass as those in exercise 10 must be hung on the hanger to cause the neck to remain permanently stretched (i.e., plastically deformed) after the coats are removed?

Exercise 10

A coat hanger is made from polyvinyl chloride. The neck of the coat hanger is 0.01 m in diameter and initially is 0.10 m long. A coat hung on the coat hanger causes the length of the neck to increase by 1.0 × 10^-5 m. What is the mass of the coat? The stress–strain diagram is provided.

Properties of PVC 50 40 0.10 m 0.010 m dia. 30 20 10 O 0.01 0.02 0.03 0.04 Strain