Finding Shear Strain: Step-by-Step Guide

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Homework Statement

A square steel plate is 10.0 cm on a side and 0.500 cm thick.
Find the shear strain that results if a force of magnitude $9.0\times10^5N$ is applied to each of the four sides, parallel to the side. Plate is in equilibrium.
Find the displacement x in centimeters.

Relevant Equations

Shear stress $=\frac FA$, shear strain $=\frac xh$, $S_\text{steel}=7.5\times10^{10}$

$$S=\frac FA\frac hx\Leftrightarrow\frac{F}{SA}=\frac xh=\text{shear strain}\\
\frac xh=\frac{9.0\times10^5}{10.0\times0.500\times10^{-4}\times7.5\times10^{10}}=1.2\times10^{-3}\\
x=1.2\times10^{-3}\times0.500=6.0\times10^{-4}\,cm$$
I'm doing something wrong, any help?

 

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Both my answers are off by a factor of 2. Applying a force to two sides is equivalent to $\text{Sheer stress}=2\frac FA$? I think that I have been mislead by this: