Elastomer stretched in tension and elongation

[tone999]

Homework Statement

A strip of elastomer was stretched in tension and elongation and was held constant. After 10 minutes the tensile stress in the specimen dropped by 12%. Assuming that the elastomer behaves in accordance with the maxwell model:

(i) Calculate the relaxation time (to the nearest whole number)
(ii) Show that it takes 22 minutes for the stress to drop to 75% of its final value.

Homework Equations

The Attempt at a Solution

I take it we have to use the maxwell model equation here?

sigma (t) = sigma (0) e ^ -t/tau

 

[Redbelly98]

The Attempt at a Solution

I take it we have to use the maxwell model equation here?

sigma (t) = sigma (0) e ^ -t/tau

I think so. Based on the information in the problem statement, what is the ratio,

sigma(t) / sigma(0),​

when t=10 minutes?