The principle of the lever -- a simple teeter-totter
An object that rotates about a fixed point or about an axis because of a force being applied to it has torque.
Torque is proportional to the applied force and to the perpendicular distance at which this force acts from the given point or axis.
- Objects in static equilibrium must satisfy the condition that all forces acting on its center of mass must add up (vectorially) to zero.
- This condition makes sure that all forces that are pulling or pushing the object from one side to the other are balanced.
- There is also another condition that must be met so that the object is in true static equilibrium.
- All torques acting on the center of mass of the object must add up to zero.
- This ensures that the object does not undergo any rotation.
Conditions for static equilibrium:
- The sum of all translational forces = zero
- The sum of all rotational forces = zero
Solutions to Static Equilibrium Problems
From the Free Body Diagram:
(Taking torques about point A)