# Homework Help: Thermal expansion (easy)

1. Nov 18, 2013

### nickb145

1. The problem statement, all variables and given/known data

A 61.00m long steel measuring tape is calibrated for use at 20.0∘C. How long is this tape under the following conditions:

a hot day with 38∘C?
Express your answer using four decimal places and include the appropriate units.
i've been losing my mind over this, i swear i'm doing it correctly.

2. Relevant equations

ΔL/L=αΔT

3. The attempt at a solution

(38-20)=18°C

(61m)(1.2*10-5)(18)= .01317m

Mastering physics keeps telling me that I'm inncorrrect , I swear i'm doing it how the book wants me to do it.

2. Nov 18, 2013

### TSny

Is this the length of the tape or the change in the length of the tape?

3. Nov 18, 2013

### nickb145

it is the change in L

Last edited: Nov 18, 2013
4. Nov 18, 2013

### Staff: Mentor

Does it make sense that a 61 meter long steel tape shrunk to about 1.3 cm in length?

5. Nov 18, 2013

### nickb145

obviously not.

6. Nov 18, 2013

### Staff: Mentor

So. What is it that your formula is giving you?

7. Nov 18, 2013

### nickb145

the ammount the metal is changing in length. Silly me, i didn't add it together

8. Nov 18, 2013

Huzzah!