- #1

JustinLiang

- 81

- 0

## Homework Statement

I need help specifically with b.

The inner diameter of a steel ring is 2.0000 cm, and the diameter of an aluminum

disk is 2.0100 cm. Both are at 430 C. At what common temperature will the disk fit

precisely into the hole in the steel ring?

**b) If after the aluminum disk is fitted precisely**

into the hole the two metals are the temperature is changed to 200 C, what is the stress

in the steel ring?

into the hole the two metals are the temperature is changed to 200 C, what is the stress

in the steel ring?

## Homework Equations

deltaL=a*Lo*deltaT

deltaL=F*Lo/Y*A

## The Attempt at a Solution

I have attached my attempt. I would like to know if it makes sense to have the change in length of the steel=change in length of the aluminum. Thus we can solve for the stress in between.

What my friend did was have the change in length of the steel=negative change in length of the aluminum. Meaning that he would have two negative signs, one for each of the change in lengths in my first equation. I told him this is wrong because by doing so, he is assuming the the overall change in length of the system is zero. This is not the case because there are no rigid supports preventing the rings from expanding. Therefore, the ring and disk will be bigger.

#### Attachments

Last edited: