Chapter 4
Newton's Three Laws
Part 16

Static Equilibrium

When external forces act on a body resulting in no change of motion then the body is in equilibrium. Under Newton's Second Law if there is no change in motion the acceleration is zero. Which also means the sum of all the forces is zero. The First Condition of Equilibrium is:

and if we resolve the vectors into perpendicular component vectors:

Parallel Force Systems

When a mass is attached to a rope so that it hangs there is tension on the rope. If there is only one rope the weight of the mass is equal to the tension in the rope.

If there is more than one rope supporting the mass then we can use the idea of a force-multiplier. As the figure show the weight is distributed among the ropes.

Now for some Static Equilibrium examples.