What Are the Calculations for the Orbit of Vanguard 1 Satellite?

[Longee]

So for an online quiz, I am stuck on this question:

The oldest artificial satellite still in orbit is Vanguard I, launched March 3, 1958. Its mass is 1.60 kg. Neglecting atmospheric drag, the satellite would still be in its initial orbit, with a minimum distance from the center of the Earth of 7.02 Mm and a speed at this perigee point of 8.23 km/s.

(a) For this orbit find the total energy of the satellite–Earth system.

(b) For this orbit find the magnitude of the angular momentum of the satellite.

(c) At apogee, find the satellite's speed and its distance from the center of the Earth. (c1) Distance from the center of the Earth

(d) Find the semimajor axis of its orbit (metres)

(e) Determine its period (minutes)

For A) I subtracted U by Ek and got an answer of -9.0788x10^19 J

For B) I got 9.244x10^-5 Kgm^2/s Are my answers correct so far? I only have one more try on the questions.

 

[Simon Bridge]

Welcome to PF;
We shouldn't be doing your quiz for you. So how can you become confident in your answers without having someone else tell you if you are right or not?
Well, you can check the consequences:
For (a), if I read you right, you are saying that the total energy is the potential energy less the kinetic energy: E=U-K
Would you expect the total energy to be conserved? So what would you expect to happen to the kinetic energy if the satellite were to move closer to the Earth (losing potential energy)? What does the above relation tell you?

For (b) I cannot tell because you have not shown your reasoning. However, you should be able to check by the same approach as for (a).