Strain in Different Directions: Understanding Tensile Forces on Cubes

[chetzread]

Homework Statement

the tensile force is applied at x direction to the cube , the cube will decrease in size in y and z direction , right ?
according to notes,
the strain in x direction εx = σxy/ E , where σy = normal stress in y direction , [/B]

Homework Equations

The Attempt at a Solution

Which is correct ? I think the εx = σx / E make sense , so i think it's correct , because the force is applied in x direction .
Correct me if i am wrong

 

[Chestermiller]

Get rid of this horrible book. There are typos in 2 out of the 3 equations it presents on just this single page. I will no longer answer any questions about the information in this book.