Forces in

Equilibrium

Objectives:• define statics, equilibrium,

static equilibrium ,center of gravity

• tell whether the equilibrium of a uniform object is stable, unstable or neutral

Objectives:

Are forces present in static objects?

Static Equilibrium --- a condition in which all forces acting on a body are balanced, causing the body to remain motionless

Center of Gravity---a point where the resultant force or the sum of the weights of all the particles that compose the matter are concentrated

Where C.O.G. is locatedGenerally found in

the middle of all the weight…

Where C.O.G. is locatedDoes not even have to

be within, the object itself Ex. Boomerang

Where C.O.G. is located MAY be located toward one

side of an object where most of its mass is focused…Ex. WeeblesCOG

Weebles Wobble, but they don’t fall down???

Weebles have very low COG Objects with a low COG are

less likely to topple because of this principle

• Higher COG is, the easier to topple

Methods of locating the center of gravity

For regularly shaped objects:

---- the center of gravity is at their geometric centers

For irregularly shaped objects

---- can be found by balancing by hanging, or by using the plumb line

CG

Why is it that the leaning tower of Pisa does not topple down?

For an object to balance, and not topple… support must be directly below C.O.G.

C.O.G. --Balancing• For an object to balance, and not

topple… support must be directly below C.O.G.

Advantage of low COGAthletic advantageswrestling—harder to takedown

Advantage of low COG

Football –Both easier to drive power through their leg

Advantage of low COG Much more control in all

vehicles w/ low COG

Racing car

States of Equilibrium

1.Stable --- when the CG of an object is at its lowest possible position

2. Unstable--- when the CG is at its highest possible position

3. Neutral--- if the CG is neither lowered nor raised

Examples of stable objects

Examples of Unstable objects

Examples of Neutral objects

Factors that affect equilibrium

1. Area of the base: the bigger the area of the base, the more the stable the object is

2. Weight: the heavier the object is, the more stable it is

Which is more stable?

Balance two forks on the edge of the water glass using only a toothpick.

How does it work?The secret to this science stunt lies in your understanding of the concepts of center of gravity and stability. The center of gravity of any object is the point about which you can balance the object as if all the masses were concentrated or gathered at this point.

In other words, it's the point at which the object balances from left to right, front and back, and top and bottom. In your balancing fork act, the center of gravity is directly below the spot where the toothpick rests on the rim of the glass. If you look closely at your balancing fork-art, you'll notice that the fork handles are positioned below the toothpick.

This actually puts the center of gravity directly below the point where the toothpick is balanced (called the pivot point). Here's where it gets really strange: the center of gravity, where the forks balance front and back, left and right, top and bottom, is actually hanging in mid-air.