Equilibrium

For an object to remain in equilibrium, two conditions must be satisfied - both the net force and the net torque must be equal to zero.

SF = 0

St = 0

An example of an object in equilibrium is a rod that is free to rotate about a hinge at one end. It is held horizontally, with the torque due to the force of gravity being balanced by the torque from a force with a vertical component applied at some point along the rod.

For the rod to remain in equilibrium, note what happens to the force as it is moved further from the hinge. Note also the hinge force.

Note also what happens as the direction of the force is varied, but with the force being applied at a fixed position on the rod.