Easy HS physics problem

[juancferrer]

I've got this friend taking HS physics, and the teacher gave him this extra credit/bonus problem, and he's not too sure how to solve it, so i thought that some of you guys (and couple of girls) could help him out. Anyway, here's the problem:
How far away from the earth does a rocket have to be before it can turn its engines off, and be pulled to the moon with its gravity?

 

[Heisenberg]

It will be the point where the earth's force of gravity is equal to that of the moon's. Set the two equations equal to each other, and solve for the distance.

 

[Ionizer86]

Yea, Heisenberg's got it; no uncertainty principle needed here

 

[eLiu]

Originally posted by: Ionizer86
Yea, Heisenberg's got it; no uncertainty principle needed here

HAHAHAHAHA...omg...that's so lame...yet so funny..hahahahaha

 

[Chaotic42]

Originally posted by: Ionizer86
Yea, Heisenberg's got it; no uncertainty principle needed here

Just don't calculate its position too well.

 

[LordMorpheus]

Originally posted by: juancferrer
I've got this friend taking HS physics, and the teacher gave him this extra credit/bonus problem, and he's not too sure how to solve it, so i thought that some of you guys (and couple of girls) could help him out. Anyway, here's the problem:
How far away from the earth does a rocket have to be before it can turn its engines off, and be pulled to the moon with its gravity?

Are you counting the momentum of the rocket in with all this? This could be quite complicated if you were actually attempting this: acceleration due to the rocket (continuously increasing because earth's grav is getting smaller and mass is getting smalled cause fuel is being burned) and at one point signifigantly before the point of equilebreum the rocket could shut off and be going fast enough to just coast on over.

But, as far as the class is concerned, just give him the point of equilebreum. I kin spele.

 

[juancferrer]

Thanks Hiesenberg, my friend tried to explain to me how he was trying to solve it, and he said he was going to have a proportion, or something like that, so maybe he was doing the right thing all along. Also, this is a HS class, so i don't think that they are going to have to figure out everything that LordMorpheus is talking about, but i do see where that could make finding the answer alot more difficult...I'll relay the answer to my friend, Thanks all.

 

[Heisenberg]

Originally posted by: LordMorpheus

Originally posted by: juancferrer
I've got this friend taking HS physics, and the teacher gave him this extra credit/bonus problem, and he's not too sure how to solve it, so i thought that some of you guys (and couple of girls) could help him out. Anyway, here's the problem:
How far away from the earth does a rocket have to be before it can turn its engines off, and be pulled to the moon with its gravity?

Are you counting the momentum of the rocket in with all this? This could be quite complicated if you were actually attempting this: acceleration due to the rocket (continuously increasing because earth's grav is getting smaller and mass is getting smalled cause fuel is being burned) and at one point signifigantly before the point of equilebreum the rocket could shut off and be going fast enough to just coast on over.

But, as far as the class is concerned, just give him the point of equilebreum. I kin spele.

It wouldn't be that hard. You'd just have an extra time-dependent force term in the equation. But for HS physics, I'm sure they are just looking for the equilibrium point.