$3.$ Draw a unit square.

$3\mathrm{.}1.$ Draw the square subject to rigid body rotation.

$3\mathrm{.}2.$ Draws the square subject to a horizontal displacement field.

$3\mathrm{.}3.$ Draws the square subject to a vertical displacement field.

$3\mathrm{.}4.$ Draw the square subject to a shear displacement field.

$($mechanics of the continuous medium$)$