Chapter 10

Center of Gravity

10.1 Center of Gravity

• Center of Gravity – (CG)

the point at the center of its weight distribution

10.1 Center of Gravity

10.1 Center of Gravity

• CG’s follow a smooth parabolic pathway when the object is thrown through the air

10.2 Center of Mass• Center of Mass – point at the

center of an object’s mass distribution, where all its mass can be considered to be concentrated.–(generally the same as center of

weight)

10.3 Locating the Center of Mass

• For a uniform object:

–find the geometric center or midpoint

•also known as the balance point

10.3 Locating the Center of Mass

10.3 Locating the Center of Mass

• The CG of an object may be located where no actual material exists.–For example, where is the CG of a doughnut?

10.4 Toppling

• Rule for Toppling:–If the CG of an object is above the area of support, the object will remain upright. If the CG extends outside the area of support, the object will topple.

area of support

Why does a football player stand with both

feet apart?

Why does a football player stand with both

feet apart?

to increase the size of his support base

Why does he bend his knees?

Why does he bend his knees?

to lower his CG

10.5 Stability

• Unstable Equilibrium – the state of an object balanced so that any small displacement or rotation lowers its CG–(EX: paper cone on its tip)

10.5 Stability

• Stable Equilibrium – the state of an object balanced so that any small displacement or rotation raises its CG–(EX: paper cone on its base)

10.5 Stability

• Neutral Equilibrium – the state of an object balanced so that any small movement neither raises nor lowers its CG–(EX: paper cone on its side)

What happens to the CG of a building that has

structure below ground?

What happens to the CG of a building that has

structure below ground?

What happens to the CG of a building that has

structure below ground?

It lowers causing greater building stability.

10.6 Center of Gravity of People

Different people have different CG’s.

EX: men and women have different CG’s due to weight distribution

Chapter 10 Key Terms• Center of gravity

• Center of mass

• Neutral equilibrium

• Stable equilibrium

• Unstable equilibrium