@experimentX

- anonymous

@experimentX

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- anonymous

Let's start with Keplers laws

- anonymous

Let's see what I remember without looking at my cheat sheet

- anonymous

Something about
\[T^2=R^3\]

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## More answers

- experimentX

seems like I forgot Kepler laws ... let's see

- anonymous

The period of an object orbital around the sun is proportional to the radius?

- anonymous

whose radius? or perhaps some distance? The distance between that object and the sun?

- experimentX

http://en.wikipedia.org/wiki/Kepler's_laws_of_planetary_motion
ellipse ... semi major axis.

- anonymous

no cheating haha

- anonymous

:P

- anonymous

draw it with me|dw:1361862577312:dw|

- experimentX

|dw:1361862616815:dw|

- anonymous

Let's see what I remember about the semi major axis.......

- DLS

\[\LARGE (\frac{T_1}{T_2})^2=(\frac{R_1}{R_2})^3\]

- DLS

\[\LARGE \frac{dA}{dT}=\frac{L}{2M}\]

- anonymous

why do we have two semi major axis?

- anonymous

what ratio is that?

- experimentX

it doesn't matter which side you take ... lol

- anonymous

|dw:1361862832161:dw|

- anonymous

|dw:1361862878591:dw|
Where is \(R_2\)

- experimentX

http://en.wikipedia.org/wiki/Semi-major_axis

- anonymous

>:O

- anonymous

wiki didn't explain the ratio though

- anonymous

LOL I'm tired. ok I get it

- anonymous

Let's talk about escape speed

- DLS

\[\LARGE \sqrt{2gR}\]

- anonymous

|dw:1361863110279:dw|
sweetheart, I have all the formulas staring at me from my notebook. I'm trying to have a discussion about those wonderful formulas

- anonymous

something about when the kinetic energy reaches \(\frac{GMm}{r^2}\)?

- experimentX

|dw:1361863195805:dw|

- anonymous

THanks! When do we know we have reached escape speed?
\[U_f+K_f=U_i+K_i\]
Let's derive escape speed.
we don't have a final kinetic energy when we've reached escape speed correct?

- DLS

\[\frac{-GMm}{R}+\frac{mv^2}{2}=0\]

- DLS

put the total energy=0
find V

- anonymous

Why what's the logic behind it?
WHy is the total energy zero?

- DLS

If a body's total net mec. energy=0,it will escape from the earth's gravitational field

- experimentX

find the total work done when bringing object from infinity to position 'r'

- anonymous

oh ok, so when the kinetic energy equals the potential energy?

- DLS

have u heard of binding energy

- anonymous

Let's see if I remember. When E<0 or =0

- anonymous

parabolic and hyperbolic orbits?

- anonymous

that's when they're unbound correct?

- anonymous

nope when E>0 is unbound

- anonymous

when E is less than zero is the only time when it's bound

- anonymous

So when the potential is greater than the kinetic energy the energy is bound?

- anonymous

gotta sleep =) Thanks for the discussion everyone. I look forward to hear more about bounded and unbounded Energy when I wake up. See ya :)

- experimentX

sorry ... was kinda busy not paying attention

- experimentX

this way you can do it ... for escape velocity.
|dw:1361863974972:dw|

- experimentX

You can equate those two, and hence get the result ...

- experimentX

I think ... if the velocity is less than esc velocity, the orbit will be elliptical or circular
at escape velocity, the orbit is parabolic, and beyond that .... it's hyperbolic.

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