Gravity, mass and distance

GRAVIT

Y, M

ASS AND

DISTA

NCE

WHAT

’S T

HE ATT

RACTION?

WHAT GOES UP MUST COME DOWN

More on this later…….

GRAVITYEverything in the universe has itEverything is attracted to

everything elseYou are are attracted to your

homework, your homework is attracted to your calculator, your calculator is attracted to your pencil and your pencil is attracted to you!

If everything is so attractive, WHY DON’T YOU DO YOUR HOMEWORK?

What is it?

GRAVITY

The strength of this attractive force (gravity) depends on only two things, the

MASS of any two objects

and theDISTANCE between

the centers of those objects

WHAT IS THIS ATTRACTIVE RELATIONSHIP?

One is very simple: the relationship between mass and gravity.

The greater the mass, the greater the force of gravity – pure and simple! It is a direct relationship

For example, if an object has 5 times more mass than another object, the first object will exert a force of gravity 5 times greater.

GRAVITY AND MASSWhich mass exerts a greater force of gravity and why?

JUST THE OPPOSITE

The relationship between distance and gravity is a little more complicated.

As the distance between the objects increases, the force of gravity decreases. This is a type of indirect (or inverse) relationship

The farther apart objects are, the less attractive they are to each other.

BUT WAIT, THERE’S MORE!

Here is the complicated part: If the distance between the objects increases by 3 times, the force of gravity decreases by 9 times

Can you figure out the mathematical relationship between 3 and 9?

The same relationship exists between

4 and 165 and 25

“PHYSICS TALK”

This is referred to as the inverse square law

The gravitational effect between objects varies inversely to the square of the distance between them.

Huh?

“SIMPLE TALK”

As the distance between two objects get LARGER, the force of gravity between them gets smaller.

YOU TRY

How does the force of gravity change?

1

2

Does the force of gravity decrease by

a. 1/2 b. 1/4 c. 1/3

LET’S SUMMARIZE

WHAT GOES UP MUST COME DOWNDown is toward the center of the mass

Up is the other way

Goes and Comes means the motion of the What has been changed

Must means it has no choice!

Why no choice?

ANY QUESTIONS?