Why Is Longitudinal Strain Zero for a Heated Copper Rod on a Smooth Surface?

[REVIANNA]

Homework Statement

A copper rod of length l_0 at 0 C is placed on a smooth surface.Now the rod is heated up to 100 C.FIND THE LONGITUDINAL STRAIN DEVELOPED ?

The Attempt at a Solution

What I did :
strain = delta l/ l_0
= l_0 alpha(coefficient of linear expansion) delta T/l_0
=100 alpha

but surprisingly the answer is zero and the solution says since the "SURFACE IS SMOOTH".
I have no clue why or how it works?

 

[billy_joule]

I agree with your answer. The given answer makes sense if the question asked for longitudinal stress, so it may be a typo.

 

[Chestermiller]

I agree with your answer. The given answer makes sense if the question asked for longitudinal stress, so it may be a typo.

Ditto.