ahh need ap physics c help :(

[Wheatmaster]

i keep trying but i get the wrong answer:

A satellite of mass 300 kg is in a circular orbit around the Earth at an altitude equal to the Earth's mean radius. Find (a) the satellite's orbital speed, (b) the period of its revolution, and (c) the gravitational force acting on it.

a. (mv^2/r)=GmM/d^2 v=sqrt((6.67x10^-11)(5.98x10^24)/(6.37x10^6)=7.9x10^3m/s
answer is 5.59x10^3m/s?

 

[NutBucket]

man, that's so 5 years ago:Q

 

[MichaelD]

It's going really, really fast and weighs a whole lotta frickin' tons and stuffz. Really. Like one BEEELIION...stuffz.

 

[Tweak155]

use 2x the radius because it that is the distance it is from the center of the earth

 

[Wheatmaster]

Originally posted by: Tweak155
use 2x the radius because it that is the distance it is from the center of the earth

whoa thats right but why is it 2x the radius? i don't understand. isn't the center of the satellite to teh center of the earth the radius of the earth?

 

[NutBucket]

No, because the distance from the surface of the earth to the satellite is the same as the radius of the earth. Therefore, from the center to the surface of the earth is one radii, from the surface to the satellite is another radii. So try 2R.

 

[Wheatmaster]

Originally posted by: NutBucket
No, because the distance from the surface of the earth to the satellite is the same as the radius of the earth. Therefore, from the center to the surface of the earth is one radii, from the surface to the satellite is another radii. So try 2R.

oooo i read it wrong dohhh

ok for b.

i'm trying: 2(pi)r=vT

2(pi)r=(5.59x10^3)T

 

[Tweak155]

Originally posted by: NutBucket
No, because the distance from the surface of the earth to the satellite is the same as the radius of the earth. Therefore, from the center to the surface of the earth is one radii, from the surface to the satellite is another radii. So try 2R.

 

[Tweak155]

EDIT: im blind

 

[Tweak155]

Originally posted by: Wheatmaster

Originally posted by: NutBucket
No, because the distance from the surface of the earth to the satellite is the same as the radius of the earth. Therefore, from the center to the surface of the earth is one radii, from the surface to the satellite is another radii. So try 2R.

oooo i read it wrong dohhh

ok for b.

i'm trying: 2(pi)r=vT

2(pi)r=(5.59x10^3)T

isnt period just 2(pi)r?

er wait, no you have it right, you are getting the wrong answer?

 

[Wheatmaster]

Originally posted by: Tweak155

Originally posted by: Wheatmaster

Originally posted by: NutBucket
No, because the distance from the surface of the earth to the satellite is the same as the radius of the earth. Therefore, from the center to the surface of the earth is one radii, from the surface to the satellite is another radii. So try 2R.

oooo i read it wrong dohhh

ok for b.

i'm trying: 2(pi)r=vT

2(pi)r=(5.59x10^3)T

isnt period just 2(pi)r?

er wait, no you have it right, you are getting the wrong answer?

nm i got it. for c, is the formula just mv^2/r?

 

[Tweak155]

as for c:

I belive it is just the gravitational constant between the 2, dont remember the formula you use

 

[Tweak155]

Originally posted by: Wheatmaster

Originally posted by: Tweak155

Originally posted by: Wheatmaster

Originally posted by: NutBucket
No, because the distance from the surface of the earth to the satellite is the same as the radius of the earth. Therefore, from the center to the surface of the earth is one radii, from the surface to the satellite is another radii. So try 2R.

oooo i read it wrong dohhh

ok for b.

i'm trying: 2(pi)r=vT

2(pi)r=(5.59x10^3)T

isnt period just 2(pi)r?

er wait, no you have it right, you are getting the wrong answer?

nm i got it. for c, is the formula just mv^2/r?

It should be something with 2 masses in it, not just one, i totally forget the formula but you need the gravitational constant in it

 

[Wheatmaster]

Originally posted by: Tweak155
as for c:

I belive it is just the gravitational constant between the 2, dont remember the formula you use

ooo got it thanks alot