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.

ΣF = 0

Στ = 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.

What, if anything, happens when the upward force F is moved a little to the right, away from the hinge? To maintain equilibrium:

1. The magnitude of the upward force F increases.
2. The magnitude of the upward force F decreases.
3. The magnitude of the downward hinge force increases.
4. The magnitude of the downward hinge force decreases.
5. Both 1 and 3
6. Both 1 and 4
7. Both 2 and 3
8. Both 2 and 4
9. None of the above.

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.