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Gravity Review
What would have to happen to the
Earth for its gravity to increase?
It’s mass would have to increase.
Why? Gravity is directly related to
the amount of mass and the
distance between two objects.
What is the difference in the
amount of gravitational force a
bowling ball would exert vs. a
tennis ball?
Since a bowling ball has more
mass, it would exert a greater
gravitational force than a tennis
ball. Again, more mass – more
gravity
What two conditions determine
the amount of gravitational force
experienced between two objects?
The amount of mass of each of the
objects and the distance between
them.
The first masses have more
gravitational force between them even
though they are the same size because
they are closer to each other.
1.
2.
The second pair of masses have more
gravitational force between them
because that pair has more mass.
1.
2.
What happens when a
gravitational force is balanced,
meaning equal with another force?
When gravitational forces are
balanced there is no movement.
Example: The clock on our wall
does not fall because the force of
the wall hook holding it up is equal
to the gravitational force pulling
down
Balanced forces = no movement
What happens when a
gravitational force is unbalanced,
meaning unequal with another
force?
There is movement of some type.
Example: If I pushed the clock (adding
my force to that of the hook), the
forces would be unbalanced and the
clock would move upward. If it moved
enough to dislodge from the hook, it
would continue to be unbalanced and
gravity would win (unless I caught the
clock)
Unbalanced forces = movement
What objects exert a gravitational
force?
ALL OBJECTS:
Everything with mass has gravity!
How do we measure mass?
We measure mass using a
BALANCE and we measure in units
called GRAMS.
We measure weight with a SPRING
SCALE and we measure in units
called grams called NEWTONS
How fast do objects fall due to
gravity?
All objects fall with the same
acceleration regardless of their
masses. On Earth that means all
objects fall 9 meters for every
2
seconds or 9.8 m/s (which means
nd
the 2 second they fall 9.8 + 9.8 or
19.6 m/s and the 3rd second 9.8 +
9.8 + 9.8.
Is there a point where a falling
object quits accelerating?
Yes, objects stop falling when they
reach terminal velocity. At that
point they just continue to fall at
the same rate. Example: once a
human reach 53 – 56 m/s they quit
accelerating.
What is free fall?
Free fall is when there is no air
resistance and only gravity is
pulling it down. Example:
astronauts inside the space shuttle
have no air resistance, just very
light gravity
What is projectile motion?
Projectile motion is the curved
path an object follows when
thrown or propelled near the
surface of the Earth.