stupid satillites (1 Viewer)

[blueduck]

which has the greater velocity

a. low earth orbit satillite or
b. geostationary satillite?

so far ive come up with how the low earth would have to be going very fast to prevent it from falling to earth BUT the geostationary has a much larger distance to cover and so would require a very high velocity aswell...

im pretty sure there wont be a specific qu on it but u never know... examiners are fickle creatures

 

[untouchablecuz]

low Earth orbit son

v=√(GM/r)

v oc 1/√r

 

[blueduck]

many thanx "insert patronising name here"

 

[00iCon]

maybe you should learn to speel before the exam too.

 

[blueduck]

fcuk!

 

[gabgab]

Geostationary Orbits are at an altitude of 36000km, and have a period of roughly 24 hours of course.

Low earth orbits are at an altitude of between 250 and 1000km, and their period varies between 90 minutes and 5 hours.

i kinda just tried to work it out, and i think, if i've done it right, which i probably havent, it depends on the period of the low earth orbit and the position its at.

i just dont know. i tried.

 

[blueduck]

what formula are u using?
v=√(GM/r) says that period is irrelevant
but the ever so lovable d=st says that it is

btw is v=√(GM/r) a derivation of r^3/T^2=GM/4pi^2 ? bastard isn't in the given formula sheet

 

[00iCon]

btw is v=√(GM/r) a derivation of r^3/T^2=GM/4pi^2 ? bastard isn't in the given formula sheet

Gravitational potential energy = Kinetic energy
work from there...

 

[helper]

Gravitational potential energy = Kinetic energy
work from there...

No that is for escape velocity.

This one is based on centripetal force = gravitational force. (doesn't have the 2 in it)

 

[untouchablecuz]

btw is v=√(GM/r) a derivation of r^3/T^2=GM/4pi^2 ? bastard isn't in the given formula sheet

for orbital velocity, equate centripital force and gravitational force

F_c=F_g
mv²/r=GM_planetm/r²
v_orbital=√(GM_planet/r)

keplers third law is a consequence of this; let, in the above equation, v_orbital=2πr/T to derive it

make sure you understand how to derive the former

what formula are u using?
v=√(GM/r) says that period is irrelevant
but the ever so lovable d=st says that it is

the issue with this equation is that it is multi variable

what i mean by this is that in v_orbital=2πr/T (d=vt), [r, T and v] are not constant

if r increases, then T will change such that the equation remains true, causing v to change etc etc

so we cannot say that v oc r

in v=√(GM/r), the only variables are v and r, and so there is direct proportionality between v and 1/√r

correct me if i'm wrong helper or darkchild