# Gravity Review Sheet Answers: by DI0rR5B

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```									Gravity Review Sheet Answers:

Review: Gravity

Whenever we tell how fast or slow something is going, we tell how
far the object will move in a given time, such as miles per hour or
meters per second. This is called the object’s speed. When we
also tell in which the direction the object is traveling, we now
refer to its movement as its velocity. How much this changes over
time, whether it is an increase or decrease, is known as the
object’s acceleration. For example, for a falling object in a vacuum,
it is 9.8m/s/s.

Mass and weight are not exactly the same. Mass refers to the
amount of matter in an object, while weight is a measure of gravity on
the object. In the metric system, weight is expressed in newtons
while mass is expressed in kilograms.

In ancient times, the famous Greek philosopher Aristotle stated
that heavy objects fall faster than lighter objects. This idea was
finally questioned by the Italian scientist Galileo,, who said that in a
vacuum (to avoid air      resistamce), all objects will fall at the same
rate.

He proved this by using weights tied to a string that he would
swing back and forth. This device is called a pendulum. In the
experiments we did in class, we discovered that the only variable
which affects the period of a swinging object was the
length of the string.

In 1665, another scientist, Isaac Newton, was supposedly sitting
under a tree and watched an apple fall, and while looking at the   moon
in the sky at the same time, started thinking about the force of
gravity. He came up with the Law of Universal Gravitation, which stated
that the force of gravity between any two objects depended on
the mass of the two objects and the distance between them.

To calculate how fast objects fall, you use the following equation:

Δv = g x t

For example, if you went up to the top of Frost’’s roof above the
gym and dropped a penny down to the basement level, let’s say it
would take 1.5 seconds. What would the penny’s velocity be as it
hit the ground? (you wrote what g is, the acceleration of gravity,
on the first page of this review) 14.7m/s

Objects will not keep speeding up forever as the air slows a
falling object. When air finally prevents a falling object from
accelerating, we say that the object has reached its terminql
velocity.

is the condition of an object which is falling with no other
Free fall
force slowing it down. This is impossible on the earth because of
the atmosphere. Objects that are in orbit are experiencing this
condition. Astronauts seem to float, but they are really falling
around the earth.

If it were not for gravity, a satellite launched horizontally would
go straight (into space) instead of in an orbit. Gravity, since it causes
the satellite to move in a circle around the earth, is called a
centripetal force.

Since gravity decreases as you move away from the earth, satellites
orbiting the earth do not need to go as fast in their orbit as they
get further and further away. The International Space Station,
in low earth orbit, travels at a rate of about 5
miles per second; geosynchronous satellites, which orbit with the
earth’s rotation, take 24 hours to circle the earth, while earth’s
natural satellite, the moon, takes about a month to go around the
earth once.

When an object is falling as it is traveling in a horizontal
direction, it travels in a curved path; we refer to this as projectile
motion. Even though traveling, falling objects may be moving fast
(such as a shot bullet), they still fall at the same time as an object
that has no horizontal velocity-gravity “doesn’t care” if an object
is moving or not.

All objects, including you, have a point where the mass of the
object is concentrated. We call this the center of gravity. For a
regular object, this point is usually in the middle of the object,
whereas for an irregular object, it could be located just about
anywhere. For an object to properly balance (not fall over), this
point of an object must be close to the ground and above its base.

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