Notes: Name: __________________________

Stamps: Period: _____

Directions: Fill in the blanks and boxes in the note panel. After notes are done, part of your homework is to fill in the sides with study questions and write a summary that demonstrates you understand what is important in the notes.

Circular MotionQuestions/Main Ideas Main Notes

• On the Gravitron ride you feel like you are being pushed ___________

• Centrifugal Force is an ______________ force pulling you

______________

• It does _________________

• In reality, what you feel is the force of the wall pushing you ____

• Centripetal Force = force pulling you _____________ when you

move in a circle

• If circular force was centripetal which way would you fly out if the wall disappeared?

• velocity always _____________ to path

• Force and centripetal acceleration vectors are always in the _________

• Imagine: if you drove into a wall, what would you feel?

• What “threw” the driver over wall?

• _____________________________________________________

• Hard to know source when you __________ a

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NOTES NEWTON’S LAWS –CIRCULAR MOTION

• Inertia is at work in a _________ also

• The “centrifugal” outward force you feel is your ____________

• If you removed the gravitron wall you would fly out ______________ to the circular path

Centripetal Acceleration

• Imagine twirling a ball on a string

• What affects its acceleration?

1. _____________ of the twirl

2. _____________ of the string

• Now let’s mix it with Newton’s Second Law:

• Average speed can be found with _________

• Easiest to find when using the _____________ (___)• (units: ___ )

• For a circle, the distance traveled in 1 period is the ________________

• Plugging the new ____ into centripetal force gives:

ac=v2

r

v=2 πrT

Fc=mac

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ExampleImagine twirling a 0.50 kg ball on a 0.80 m long string. The ball moves in a circle at a rate of 1.25 rotations per second. How much force is required to keep the ball moving this way? What direction is this force acting in?

Summary:

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GravityQuestions/Main Ideas Main Notes

• Not everything thrown up must come __________!

• The higher something goes the ______________ the effect of earth’s gravity on it.

• If you throw it hard enough, “g” becomes too __________ to slow it to

a ___________.

• This is called the ___________________

• Escape velocity from earth = ___________________ mph

• Gravity is not only caused by large _____________, ____________

and ___________.

• Everything with __________ attracts everything else with _________

no matter the distance

• Unless the mass is _____________________, you will not notice it

Anthrocentric Universe

• Aristotle reasoned that all objects wanted

to be at the _________ of the universe…

• The ____________!

• all objects circle ____________

Heliocentric Universe

•Copernicus noticed that the planets did not stay the same ___________ from the earth.

•He used ___________________ to come up with a new theory.

•All objects circle the _________

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Tycho and Kepler

• Tycho Brahae spent ______ years trying to proves Copernicus wrong

with very careful measurements of the _____________.

• Compromise

• Planets circle both the ___________ and ___________

Universal Law of Gravity

• Isaac Newton noticed that the force making the moon go around the

earth was the same as the force causing an _________________.

• “Between any two masses there exists an attractive force of gravity

that is proportional to the product of the _____________ and

inversely porportional to the square of the _______________ between

their ________________.”

• This gives the expression:

• or, the equation

• where G = universal gravitational _______________

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Gravitational Constant

• Newton never was able to calculate “____”

• Because, If you rearange the equation to calculate G:

G =

• You find that measuring each of the variables is easy until you get to

____________.

• The force between materials on earth was too __________ for Newton to detect.

• Henry Cavendish used an apparatus made by John Michell.

• Used _____________ lead balls.

• Force of gravity can be found by measuring the tiny _________ the small balls moved

• Cavendish’s main reason to calculate G was to use it to find the

_________ of the __________.

• Imagine any object on the Earth’s surface. It’s force due to gravity

(FG) is _____.

• Since height of any object on Earth is negligible, R is just

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Earth’s _______________.

• The radius of the Earth had been calculated way back in ___________

Summary:

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Rearth=6 . 37 ´ 106m

Satellite MotionQuestions/Main Ideas Main Notes

• Imagine standing on a really tall building and throwing a ball really hard

• The ball would follow a _______________ path and land in front of the building

• Now throw it ___________.

• Same thing except balls goes a

little __________.

• If you throw it at ________ m/s, something interesting happens.

• Once the ball goes out ________ m it will have fallen by ______ m.

• The _______________ of the earth happens

to fall at the same rate.

• The ball is ____________, but never gets closer to the Earth’s surface!

• As long as the speed doesn’t change it will freefall ___________.

• The ball is now a ____________!

Velocity of a satellite

• What is acting as the ________________ force and keeps the satellite in orbit?

• The force of ___________.

ME is the ________ of the Earth

• r is the distance from the ___________ of the Earth to the satellite

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• Let’s do the same thing in terms of ____________ now (___)

Remember: • the units for period should

always be _____________

• Works for other __________ if you change ME to the planet’s mass.

Weightless Astronauts?

• Why do astronauts feel weightless in space?

• Do they really have almost no weight?

Lets see…

• First, let’s calculate the weight force on Earth of a 70 kg astronaut:

given:

• Next, let’s calculate the astronaut’s weight in orbit on the space station (380 km high)

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• ______ N vs _______ N

• Astronaut on space station still has about _____% of his weight.

• Astronauts are actually _______________ with the space station.

• Imagine an amusement park ride that never stops _____________. Yup, that’s what it’s like in space. (Vomit Comet)

Geosynchronous Orbit

• In order for communication satellites to be useful they

have to be _______________

• They are always above the same point on Earth and

appear ______________

• Actually, they are freefalling with the same ___________ as the spin of the Earth (24 hours)

Dark Matter

• Remember, we can find the mass of something by observing the

_________ and _________ of its orbiting satellites

• So, if we observed a star in a galaxy we could calculate the _________ of the galaxy.

• You can also get the mass of a galaxy using __________________.

• ____________________ can be converted to number of sun-sized stars

and then _____________.

• This was done in _________

• The stars in the Andromeda galaxy move way too fast compared to its brightness.

• Scientists concluded that there must be some

_____________________ matter.

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• Other ______________ give the same phenomenon.

• Over _____% of the universe appears to be made of this dark matter.

• The dark matter appears to stretch much further than the ___________ themselves.

Summary:

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