Equilibrium

An object is in Equilibrium if… The net force and the net torque on it are _______ Therefore, it is not linearly or angularly _____________ or The linear and angular momentum are __________

An object is in Equilibrium if… The net force and the net torque on it are zero. Therefore, it is not linearly or angularly accelerating or The linear and angular momentum are constant

Dynamic (v=constant) Static (v=0) Unstable Stable Types of equilibrium: Dynamic (v=constant) Static (v=0) Unstable Stable

The Center of Gravity The gravitational force the planet exerts on an object acts on ALL parts of the object. The object behaves like the gravitational force is acting on only ONE place – the Center of Gravity Stable objects have the cog within the perimeter of the base of the object. Objects can be more stable, or less stable, based on the width of the base.

Solving Equilibrium Problems: SFx = 0 SFy = 0 SFz = 0 St = 0 (we will only deal with equilibrium in 2 dimensions)

Examples P345 #9,2 Ladder example (next slide) P347 #23,27 Assignment: Problems (NOT questions) page 345-347 #8,3,11,7,15,13,17,30,21,28

Ladders and Equilibrium Ex: What is the shallowest angle a ladder can rest (against a wall) maintaining equilibrium, before the base slides? Assume the coefficient of static friction with the ground is ms and the supporting wall has no friction. The mass of the ladder is M and its length is L. What happens then, when a person climbs on and up the ladder?