Circular Motion: Homework on Force, Acceleration, Velocity

[runningirl]

Homework Statement

You'replanning a mission to Mars and wish to put your satellite, which has a mass of 2000 kg, i orbit around Mars at an altitude of 300 km. Mars has a mass of 6.42*10^23 kg and a radius of 3400 km.

a) What's the force of gravity acting on the satellite while it is in orbit?
b) What's the acceleration?
c) The velocity?

Homework Equations

F=GMm/r^2
F=mv^2/r

The Attempt at a Solution

for part a:

since G=6.67*10^-11
F=(6.67*10^-11)(2000)(6.42*10^23)/(3400+200)^2
=6255865595 N?

b) F=ma
6255865595=2000(a)
a=3127932.798 m/s/s?

i wasn't sure if i did parts a and b right so i didn't move onto c yet.

 

[JaredJames]

For part a:
Convert km to m for radius values.
The question specifies an altitude of 300km but your calculations uses 200km?

For part b:
What acceleration are you looking for?

For part c:
Orbital Velocity = SquareRoot(GM/r)
where r is the distance from the satellite to the centre of the planet, M is the mass of the planet and G as above.

Jared

 

[runningirl]

For part a:
Convert km to m for radius values.
The question specifies an altitude of 300km but your calculations uses 200km?

For part b:
What acceleration are you looking for?

For part c:
Orbital Velocity = SquareRoot(GM/r)
where r is the distance from the satellite to the centre of the planet, M is the mass of the planet and G as above.

Jared

sorry! i meant 300. but wouldn't the distance from the satellite to the center of the planet be 3400+300 because there's an altitude (for parts a and c)?

 

[JaredJames]

Correct (which is why I didn't correct your equation, just the value).

 

[Paulie323]

you have the correct equations just fix the errors Jared pointed out! now do u need help with c?