Equilibrium

What is equilibrium?

When the sum of the forces is zero in every direction, there is

no acceleration and the system is said to be in equilibrium.

What is stable equilibrium^?

If the equilibrium is disturbed the Forces work to return the system

to its previous state of equilibrium. 

What is unstable equilibrium

If the equilibrium is disturbed the Forces do not allow the system to

  return to its previous state of equilibrium so it finds a new equilibrium. 

What’s an example of stable equilibrium

If the mass is moved it will 

eventually return to its original position.

Whats an example of untsbale equilibrium

A mass balanced at the tip of a pyramid

 If the mass is moved it will not return to its original position, it

will eventually reach a new equilibrium.

How is perpendicilar components of a force used as a vector

The perpendicular components of a Force are independent. This allows us to break Forces into their components and group them with Forces in the same direction. It also allows us to use coordinate systems that make calculations easier.

ex: We have already been doing this with inclined planes.

Why are adding vectors related to finding resultant force

Adding Forces that are applied in different directions to find the Resultant Force (F_R). The Resultant Force is the one Force that would have the same effect as multiple different Forces. This isn’t really new, we did it in kinematics, most often with displacement.

Determining the one Force that is required to put a system into a state of equilibrium. This is called the Equilibrant Force (F_eq). The Equilibrant Force has the same magnitude as the Resultant Force (F_R) but is in the exact opposite direction.