Transcript Free Fall/Falling Objects Centers Explanation

F REE FALL C ENTERS
W ILL PAPER FALL L IKE A
S TONE ?

What happened?
W ILL PAPER FALL L IKE A
S TONE ?

Dropping the sheet of paper to the floor by itself will
make it move from side to side and descend slowly
because of the air resistance.

The book is heavy enough to overcome the air
friction and it drops in that short distance as if there
were no resistance.

Together, our intuition says that the paper should
stay behind the book in falling to the floor, but they
fall at the same rate because under the paper there
is no air and thus no resistance. It is as if the paper
fell in a vacuum.
T HE FALLING P ENNIES

What happened?
T HE FALLING P ENNIES

As both pennies were released at the same moment,
the force of gravity started to work on the pennies at
the same time.

The downward component of the forces working on
each of the pennies is therefore the same, and thus also
the acceleration they obtain, resulting in reaching the
floor in exactly the same time.

This is why only one loud click (first click) is heard of the
two pennies falling, regardless of the initial horizontal
force imparted on one of them.

In our case the air resistance was disregarded, because
of the relatively short distance of fall.
T HE FALLING WASHERS

What happened?
T HE FALLING WASHERS

The falling weights are all subjected to gravity. The force of
gravity imparts an accelerated motion to each of the weights.

Because the force and mass of the weights are equal, the
acceleration of each of the weights is the same.

The difference is that the further the weight falls, the greater
the velocity (v = at) of the weight when it hits the pie pan.

When the weights are placed at regular intervals, the arrival is
irregular, getting faster and faster, due to increased velocity
(acceleration of gravity X time).

The weights in the second demonstration also have equal
increasing velocity, but because of the increased distance
between weights, they arrive at even intervals.
WATER B OTTLE D ROP

What happened?
WATER B OTTLE D ROP

While you were holding the leaky bottle, gravity was pulling
both the bottle and water toward Earth, but only the water
was falling. You held the bottle against the pull of gravity.

When you dropped the bottle, both the water and bottle
were in free fall. The only force was the pull of gravity, which
acted equally on the water and the bottle.

If you poked a hole in the side of a bottle while free falling in
an elevator, or while orbiting Earth, the water would remain
in the bottle. The only force acting on the bottle and the
water is gravity.
G ALILEO

What happened?
G ALILEO

Objects in general fall toward Earth, not away from it.

Galileo Galilei showed that the mass of a falling body does
not affect its rate of fall.

All objects fall towards the Earth at the same rate, 9.8m/s/s
(negating air resistance).

https://www.youtube.com/watch?v=Z789eth4lFU
S KY D IVING
F ELIX B AUMGARTNER

What happened?
S KY D IVING
F ELIX B AUMGARTNER

After jumping from his platform at 120,000 feet,
Baumgartner fell and accelerated to the speed of
sound (343.2 meters per second or 768 miles per hour)
because of the sparse atmosphere at the high altitudes
where he released. The maximum speed he achieved is
much higher than what it would be at lower levels where
the atmosphere is thicker.

As he descended and got closer to the Earth the thickening
atmosphere actually slowed him up so he wouldn’t be
falling nearly as fast. Once his parachute opened, it's not
as if he will be going immediately from the speed of sound
to the speed of a skydiver falling with an open parachute.
He will have slowed down significantly by the time he
reaches that altitude.
R OLLER C OASTER P HYSICS

What happened?
R OLLER C OASTER P HYSICS

Examples of Free Fall…
- skydiving
- roller coasters
- elevators
- Base jumping
G ALILEO G OES TO THE
M OON

What happened?
G ALILEO G OES TO THE
M OON

Because they were essentially in a vacuum,
there was no air resistance and the feather fell
at the same rate as the hammer, as Galileo
had concluded hundreds of years before - all
objects released together fall at the same rate
regardless of mass.
F REE FALLING AND
W EIGHTLESSNESS

What happened?
F REE FALLING AND
W EIGHTLESSNESS

The astronauts experience weightlessness not because there is no
gravity. Rather, weightlessness occurs because they and their
spacecraft are free-falling in gravity. When two objects fall freely,
one can float inside the other until they both reach the ground.
The astronauts float inside the space shuttle just as water might
float inside a falling cup -- even if that cup had holes in it.

But what keeps the space shuttle from free-falling to Earth's
surface and crashing into it? A spacecraft can maintain its free-fall
for a very long period of time by traveling fast enough -- about 7.5
kilometers (4.7 miles) per second -- horizontally, so that even
though it is constantly being pulled toward Earth's surface, its
free-fall path is parallel to the planet's curvature.

How might we simulate free fall on Earth?
W HY D OESN ’ T THE M OON
FALL D OWN ?

What happened?
W HY D OESN ’ T THE M OON
FALL D OWN ?

The Moon is falling towards Earth. However, it also has
an orbital speed from the momentum gained during its
formation that allows it to fall around Earth with a
trajectory that follows the same curve as Earth's
surface. Because these paths are parallel, the Moon
perpetually falls around Earth without ever touching it.

In general, the stronger the force of gravity, the more
speed is needed to keep the planet falling around,
instead of into, the object it is orbiting. Because the
force of gravity weakens with distance, there is less
gravity farther away from the Sun, so less speed is
needed to keep an object in orbit.
T ERMINAL V ELOCITY: F REE
FALLING

What happened?
T ERMINAL V ELOCITY: F REE
FALLING

The filter that is less spread out falls faster.

The greater the surface area of the falling object, the
more air molecules the falling object strikes per
second.

An increase in the number of air molecules striking
the surface of the falling object increases the upward
force or drag on the object.

With an increase in drag, the acceleration of the
falling object decreases, as indicated by an increase in
the time it takes the object to fall.
E LEVATOR

Apply what you have learned to an elevator ride.

How do you feel on an elevator when it goes upward?
Downward? When it comes to a stop?

If you were standing on a scale in an elevator, would your
weight appear to increase, decrease or stay the same as
the elevator rises?

Would your weight appear to increase, decrease or stay
the same as the elevator descends?

Pretend that the elevator cable breaks and you are
plummeting towards the earth, would your weight appear
to increase, decrease or stay the same?

https://www.youtube.com/watch?v=mAr4VJxZLZ
w

http://howthingsfly.si.edu/sites/default/files/atta
chment/FreeFall.pdf

http://www.clayton.k12.mo.us/cms/lib/MO0100
0419/Centricity/Domain/265/Elevator_Ride.MO
V

http://academic.greensboroday.org/~regesterj/p
otl/Mechanics/Freefall/skydiving.html