Essential Question: How do mass and distance affect the gravitational pull of an object?

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Essential QuestionHow do mass and distance
affect the gravitational pull of an object?

• StandardS8P5a. Recognize that every object
  exerts gravitational force on every other object
  and that the force exerted depends on how much
  mass the objects have and how far apart they are.

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What you have learned so far
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Gravity

• Gravity is a force of attraction between objects
  that is due to their masses.
• All objects experience an attraction toward all
  other objects. This gravitational force pulls
  objects toward each other.

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Gravity

• Compared with all other objects around you, Earth
  has a huge mass. Therefore, Earths gravitational
  force is very large.
• You must apply forces to overcome Earths
  gravitational force any time you lift objects or
  even parts of your body.

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Gravity

• Earths gravitational force pulls everything
  toward the center of Earth.
• Because of this force, the books, tables, and
  chairs in the room stay in place, and dropped
  objects fall to Earth rather than moving together
  toward you.

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Unbalanced Forces
Air resistance is pushing upwards
Gravity is pulling to the ground
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What happens if you drop an elephant and a
feather at the same time?Which will hit the
ground first?
Why?
The force of air resistance is greater on the
elephant because of its size and shape.
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What if gravity was the only force acting on the
elephant and the feather?
They would both fall at the same speed due to the
earths gravity. This is known as freefall.
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Remember, all objects exert a force on other
objects.
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The Law of Universal Gravitation

• All objects in the universe attract each other
  through gravitational force.
• The size of the force depends on the masses of
  the objects and the distance between the objects.

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Gravitational Force Increases as Mass Increases

• Imagine an elephant and a cat. Which has a
  larger mass?

The amount of gravity between an elephant and
Earth is greater than the amount of gravity
between a cat and Earth. So, a cat is much easier
to pick up than an elephant.
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Gravitational Force Increases as Mass Increases
There is also gravity between the cat and the
elephant, but that force is very small because
the cats mass and the elephants mass are so
much smaller than Earths mass.
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Watch the video clip below. Turn to an elbow
partner and discuss how the video illustrates the
law of universal gravitation.
https//www.youtube.com/watch?v3Cm83yYtDns

• The moon has less mass than Earth does.
  Therefore, the moons gravitational force is less
  than Earths. The astronauts are not being pulled
  down with as much force as they would have been
  on Earth.

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The gravitational force between objects increases
as the masses of the objects increase. Arrows
indicate the gravitational force between two
objects.
Gravitational force is small between objects that
have small masses.
Gravitational force is large when the mass of one
or both objects is large.
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The gravitational force between you and the Earth
is large. Whenever you jump, you are pulled back
down by Earths gravitational force.
The reason is that the sun is so far away.
On the other hand, the sun is more than 300,000
times more massive than Earth. So why doesnt the
suns gravitational force affect you more than
Earths does?
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The gravity between the sun and the planets is
large because the objects have large masses. If
the suns gravitational force did not have such
an effect on the planets, the planets would not
stay in orbit around the sun.
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The gravitational force between objects decreases
as the distance between the objects increases.
Gravitational force is strong when the distance
between two objects is small.
If the distance between two objects increases,
the gravitational force pulling them together
decreases rapidly.
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StudyJams Gravity Inertia