# Homework Help: Need help on Thermodynamics problem: thermal expansion to be more specific

1. May 14, 2012

### Juniorphysics

Need help on Thermodynamics problem: thermal expansion to be more specific!!

A steel ring with a 2.5000in- inside diameter at 20.0°C is to be warmed and slipped over a brass shaft with a 2.5015in outside diameter at 20.0°C.
Part A:

To what temperature should the ring be warmed?

Part B:

If the ring and the shaft together are cooled by some means such as liquid air, at what temperature will the ring just slip off the shaft?

Attempt at solution:
using dL=alphaLidT
i converted the diameters to meters because i was given alpha in m/m°C. so i got d1=0.0635m d2=0.0635381m and dL=0.0000381m
i used alpha=13*10-7m/m°C
and got dT to be 45.9 but that gave me the incorrect answer

2. May 14, 2012

### Staff: Mentor

Re: Need help on Thermodynamics problem: thermal expansion to be more specific!!

Double check your arithmetic. (FYI: No need to change units for the lengths.)

3. May 14, 2012

### Juniorphysics

Re: Need help on Thermodynamics problem: thermal expansion to be more specific!!

It gave me the same answer

4. May 15, 2012

### Staff: Mentor

Re: Need help on Thermodynamics problem: thermal expansion to be more specific!!

Show your calculation. You are off by about a factor of 10.