STRESS

When a force is applied to an object the effect varies with direction. Take for instance a compressive force applied to an elastic cube like a rubber eraser. Between thumb and forefinger it can be squashed but then it bulges out sideways in directions perpendicular to the force. Not all substances bulge out sideways like this and  some even undergo a lateral contraction. . .
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https://drive.google.com/file/d/0BxPw8lRke1HBVDFFbE1Hc21EMlk/view?usp=sharing