What is Gravity

1
What is Gravity?

• Gravity is the word we use to describe the
  pull between masses.

Things with more MASS produce a greater Gravity
pull on each other.
2
Gravity controls.

• A roller coasters ride
• A divers dive
• A skiers jump
• A baseballs fall

3
What word describes how much of you there is?
Mass
4
Mass
Id eat a lot of yummy bread to gain mass!
Your mass is the amount of material that your
body contains. How can you gain mass?
5
Does something that is bigger always have more
mass?
No! Not Always!
6
Does bigger more mass?
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So, having more mass does not mean taking up more
space!
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Mass vs. Weight
Do things that have more mass always weigh more?
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Not Always!

• When you stand on a bathroom scale, the scale is
  made of springs. The farther down you push the
  springs, the higher the number on the scale. The
  number tells you your weight. On earth it is
  true that the more mass you have, the more weight
  you have.

10
Pretend That You Are in Space!
Oh where, oh where, has my weight gone? Oh
where, oh where can it be?
You are floating around. You drift over to a
floating bathroom scale and put your feet on it.
Your feet do not push down on the scale at all.
The scale shows that you weigh 0. You have lost
your weightbut did you lose your mass?
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All my body parts are still togetherso I still
have mass!
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Summing up Mass and Weight

• Your MASS is the amount of material in your body.
• Your MASS doesnt depend on where you are.
• Your WEIGHT is how much your body pushes down on
  a scale.
• Your WEIGHT depends on how much MASS you have and
  where you are.

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Law of Universal Gravitation

• All matter is affected by gravity
• The force of gravity is small between objects
  with small masses
• The force of gravity is large between objects
  with large masses
• If distance between objects is increased, the
  force of gravity decreases.