Equilibrium and elasticity

The net force on a body in translational equilibrium is zero.

The net torque on a body in rotational equilibrium is zero.

Ratio of the perpendicular force to the area on which it acts.

dimensionless.

Ratio of the normal stress to the longitudinal strain.

• linear elastic regime.

Ratio of the force parallel to the surface to the area.

Ratio of the shear stress to the shear strain.

Ratio of the pressure increase to the relative decrease in volume.