Got a couple of problems when lookin over my notes for Energy and velocity in elliptical orbits when studying for the space dynamics part of my exam next wed and been hit by a few problems:(adsbygoogle = window.adsbygoogle || []).push({});

(i)Wit v1 being the speed at the perihelion (position of closest approach, distance a(1-e) and v2 the speed at the aphelion (distance a(1+e)) and taking into account conservation of angular momentum since there is no torque acting why doe v1*a(1-e)=v2*a(1+e)?

(ii) after accepting the previous equation got one other problem after determining v1 (V1^2=GM[2/(a(1-e)) + D] where D=2E/GMm) and similarly for v2 my notes go on to say we can now form 2 equations for [v1/v2]^2 and set them equal and with a bit of manipulation gives D=-1/a hence showing a=-GMm/2E. How do i go about this?

Dont feel i can move on til other parts of the course till i gain a firm understanding of this. thanx

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Elliptical Orbits

**Physics Forums | Science Articles, Homework Help, Discussion**