What is free fall?
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Free fall- objects falling unaffected by air resistance.
On Earth we can’t fall without air resistance, but for
normal situations the numbers are realistic.
When things fall they constantly accelerate.
If we can ignore air resistance, all objects accelerate
at the same rate.
9.8 m/s2 = g (acceleration due to gravity on Earth at
sea level)
If everything accelerates at the
same rate, does that mean
everything falls at the same rate?
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Even they have a different weight?
yes
Even if they are different sizes?
yes
Even if they are different shapes?
not if you include air resistance
If you put it in a vacuum, then yes
Things that increase air
resistance.
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shape- more surface area means more air
resistance.
velocity- the faster you go, the more air
resistance (this is why meteors burn up in the
atmosphere)
The “thickness” of the air you go through
(there is less air resistance higher up in the
atmosphere)
Terminal Velocity
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Terminal velocity- the velocity at which the upward force
of air resistance equals the downward force of gravity.
Once you reach this velocity you will no longer
accelerate. (just stay at the same velocity)
Parachutes increase your surface area to increase your
air resistance in order to reduce your terminal velocity
so you don’t die when you hit the ground.
International Space Station
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A joint project from the United States and
Russia started in 1998 began construction on
the International Space Station.
The first crew arrived in 2000.
It is a lab, orbiting the planet where crews
work and do research.
It is the 4th Space Station to orbit the Earth.
Weightlessness
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People aboard the space station appear to
be weightless (They float around like there is
no gravity).
However, they are not out of Earth’s
gravitational field (gravity is still pulling on
them).
Freefall
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The space station is actually in freefall
around the planet.
That is what orbit is (constant free fall
around the planet).
It is moving so quickly forward, it clears the
planet.
Frame of Reference
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The “weightlessness” has to do with the
frame of reference.
If everything is falling at the same rate, it
appears as though it is floating with no
gravity.
Similar to being on an amusement park ride
that drops you straight down.
Weightless sensation
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If you put a penny on your knee and ride
something that drops you, like the Demon
Drop at Cedar Point, it will “float” in front of
you, at least from your frame of reference.
Really it is falling at the same rate you are.
In the case of the space station everything is
falling with you (air included), so you can’t tell
you are falling.