| Translational Equilibrium | An object is said to be in translational equilibrium when the sum of the forces acting on it is equal to zero. |
| Static equilibrium | When an object is at rest, it is said to be in static equilibrium. |
| Dynamic equilibrium | When an object moves with a constant velocity, it is said to be in dynamic equilibrium. |
| Tension | The force from a tight string, rope, or chain. This force is directed away from the object to which the string, rope, or chain is anchored. |
| Translational motion | Motion from one point to another which does not involve repeatedly passing the same point in space. |
| Rotational motion | Motion around a central axis such that an object could repeatedly pass the same point in space relative to that axis. |
| Lever arm | The length of an imaginary line drawn from the axis of rotation to the point at which the force is being applied. |
| Torque | The tendency of a force to cause rotational acceleration. The magnitude of the torque is equal to the length of the lever arm times the component of the force that is applied perpendicular to it. |
| Rotational equilibrium | The state in which the sum of the torques acting on an object is zero. |
