Notice that the moment arm, rod and line of action form a right-triangle. This is useful in determining the length of the moment arm. First determine the angle . This is the angle between the line of action and the rod. Then determine the distance between the pivot and where the force is applied along the rod.
Rotational acceleration is when something rotates faster and faster or slower and slower.
When an object has no linear acceleration and no rotational acceleration, it is said to be in equilibrium. When it isn't moving at all, it is said to be in static equilibrium. Two conditions must be satisfied for an object to be in static equilibrium. The second condition of static equilibrium concerns torque. Examine the following diagram.