Rockets (1 Viewer)

[richz]

hey i came across, a question, which i dont understand

A 75000kg spacecraft is travelling in and orbit at 5500m/s
a) how high is the spacecraft?
b) What is its kinteic energy and potential energy relative to the earth?
c) how much energy must be removed from the spacecraft during re entry?

if anyone has any ideas plz post reply thnx

 

[Jaydels]

During re-entry the spacecraft must reduce its speed by about 90%

to find height use:

v^2= Gm/r
(v=velocity, G= 6.67 x10^-11, m=mass, r=radius)
oh and you probably have to subtract the earth's radius

potential energy= -G m1m2/r
on Earth potential energy is zero

 

[richz]

During re-entry the spacecraft must reduce its speed by about 90%

is that for part c???

 

[richz]

hmm, is the answer for a) 1.65*10^-13

 

[richz]

its like so small its like on the earth

 

[Jaydels]

is that for part c???

yeah but im not really sure if it answers the question

 

[Jaydels]

Do you have the answer for the question? I think I have worked it out. We were using the mass of the satellite when we should have using the mass of the Earth.

 

[Jaydels]

Here's my working out for part a if you want it:

http://www.msnusers.com/cba9s1i0v5kq2hv7vg5cm21ja6/Documents/Pictures/physics.jpg

 

[richz]

nope, i dont have the answers, i dont have the teachers resource cd :'(

 

[richz]

Here's my working out for part a if you want it:

http://www.msnusers.com/cba9s1i0v5kq2hv7vg5cm21ja6/Documents/Pictures/physics.jpg

hmm.. this site doesnt seem to work

 

[Jaydels]

oh
can i email it to you then?

 

[richz]

ya thats fine...