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How to calculate modulus 
Note that material stress is caused by axial stretching force. 
For example, pulling straight out on a piece of taffy will stretch the taffy due to applied stress. 
Understand that material strain is caused by shearing force perpendicular to the axis of the material.
For example, pushing on the middle of a tennis racket string will bend the string due to applied strain. Measure the proportional fractional volume change (also known as dilation) of the material.