Gr. 12 Physics-Gravitational Energy Etc. I need help

[dunesquirrel]

Is there anyone who is knowledgeable to answer a few question for me?

 

[kingcomet32]

post the questions

 

[Black.Bird]

Fire away

 

[dunesquirrel]

awesome.

1) what is the total amount of energy needed to place a 2000 kg satellite in circular Earth orbit, at an altitude of 5.0 x 10^2 km?

2)A space shuttle ejects a 1200 kg booster tank so that the tank is momentarily at rest at an altitude of 2000 km. Neglecting atmospheric effects, determine:

a) how much work is done on the booster by the force of gravity in returning it to the Earth's surface?

b) The velocity with which it strikes the surface of the Earth?

2) A space vehicle, launched as a lunar probe, arrives at the upper limit of the Earth's atmosphere. At this point, its kinetic energy is 5.0 x 10^9 J and its gravitational potential energy is -6.4 x 10^9 J. What is its binding energy?

Any help is greatly appreciated! thanks

 

[bustinthejus]

2 is like grade 11 shit dude, and 1 and 3 look easy if you have the formulas, which your teacher should've given you...

 

[Black.Bird]

1) Use E=mgh.

E= (2 000 000 g)(9.8m/s^2)(500 000m)

= 9.8 x 10^12 N

 

[theabortionator]

1) 27 catfish

2) Ravioli

3)Afterbang

 

[dunesquirrel]

is two the change in kinetic energy? and for 3, Binding Energy= Escape Energy- Kinetic Energy. But how do i find the escape energy from gravitational?

 

[Black.Bird]

Sorry I don't have time to type everything but..

2) a) = 1.8 x 10^10 J

b) = 5.5 x 10^3 m/s

It's just plugging numbers in the formulas

 

[dunesquirrel]

Thanks. correct answers. what formulae did you use?

 

[Black.Bird]

For three just add the two. 5.0 x 10^9 + (- 6.4 x 10^9) = - 1.4 x 10^9

 

[Bill.Nye]

I think this should help OP

http://www.wolframalpha.com/input/?i=orbital+velocity&a=*C.orbital+velocity-_*Formula.dflt-&a=*FS-_**CircularOrbitSpeed.vc-.*CircularOrbitSpeed.m-.*CircularOrbitSpeed.r--&f3=5.98x10%5E24+kg&f=CircularOrbitSpeed.m_5.98x10%5E24+kg&f4=500+km&f=CircularOrbitSpeed.r_500+km

 

[dunesquirrel]

word thanks a lot. 10/10. i got 2 a. I guess i just miscalculated but still unsure of how you found velocity for b?

 

[Black.Bird]

for b)

Use v = Sqrt ( 2 Ke/mass)

 

[dunesquirrel]

what? i haven't even learned that. Is there any other way to do it?

 

[Black.Bird]

I don't think so?

Ke is what you calculated for a) (1.8) and I don't know what else you could use

 

[dunesquirrel]

never mind. I realized it is the same as GM/r. Thanks a lot man

 

[Black.Bird]

^No problem bud, good look with the physics. I never took grade 12 physics and took the super condensed dual physics course in first year and it sucked. Good move on your part..

 

[edai]

You're most likely in your 4th semester, does it really matter if you do your homework...

 

[dunesquirrel]

call me what you want but i do have to maintain a decently high average going into engineering and losing good work habits is probably not a good idea

 

[Darth.Maul]

Ya all of these should be able to be solved with one of the GM/r equations. I just cant remember which one is which and im taking a test on it tomorrow...

 

[jibjim]

wrong! you've got to figure out the orbital velocity and include kinetic, not just potential

 

[Black.Bird]

My bad, I'm not a physics major! at least I tried..

I've also never done anything with orbital velocity.

 

[Darth.Maul]

Orbital velocity : (GM/r)^1/2Escape velocity: (2GM/r)^1/2

Are those what you're looking for?

 

[chicken]

have they all been answered for you? If not let me know which one you need and I will show you

 

[Parks.]

Potential energy (gravitational) = mass x height x gravity (9.8 m/s)

 

[chicken]

not sure if this was said before, but that is not true. It is an approximation which works fine for small heights (like for instance throwing a bowling ball off of the leaning tower). however when you are using a large change in height (and therefor r) you will need to use the real definition.

 

[dispatchQ_main]

EASIEST CLASS, just make a crib for all the equations

 

[dunesquirrel]

all of my questions were answered. thanks a lot everyone, definitely helped and i think i did well on my test today.

 

[chicken]

the whole thing is rearranging a couple formulas. physics doesn't get hard until it gets all full of partial derivatives and surface integrals and stuff.

 

[Black.Bird]

Nightmare