Transcript Gravitational Force

Activating Strategy:
You are a professional athlete in
any sport of your choice(s). You will
be competing on a neighboring
planet that has a smaller
gravitational pull than you’re used
to. Make a list of differences that
you might encounter.
Essential Question:
How do mass and distance
affect the gravitational pull of
an object?
Standard:
S8P5a. 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.
What you have
learned so far…
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.
Gravity
• Compared with all other objects around
you, Earth has a huge mass. Therefore,
Earth’s gravitational force is very large.
• You must apply forces to overcome
Earth’s gravitational force any time you
lift objects or even parts of your body.
Gravity
• Earth’s 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.
Unbalanced Forces
Air resistance is pushing upwards
Gravity is pulling to the ground
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.
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 earth’s
gravity. This is
known as freefall.
Remember, all objects exert a
force on other objects.
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.
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.
Gravitational Force Increases
as Mass Increases
There is also gravity between the cat and the
elephant, but that force is very small because
the cat’s mass and the elephant’s mass are so
much smaller than Earth’s mass.
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?v
=3Cm83yYtDns
The moon has less mass than Earth does.
Therefore, the moon’s gravitational force
is less than Earth’s. The astronauts are
not being pulled down with as much force
as they would have been on Earth.
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.
The gravitational force between you and
the Earth is large. Whenever you jump,
you are pulled back down by Earth’s
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 doesn’t the sun’s gravitational
force affect you more than Earth’s does?
The gravity between the sun and the planets is
large because the objects have large masses. If
the sun’s gravitational force did not have such
an effect on the planets, the planets would not
stay in orbit around the sun.
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.
StudyJams:
Gravity & Inertia
Mr. Parr’s Law of
Gravity Song
Summarizing Strategy:
Refer to Earth Science where
learned about planets and
gravitational pull towards the
Sun. List any 5 different planets
and place them in order based
on decreased gravitational pull.