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## Main Question or Discussion Point

SO the equations for the speed at the aphelion and perihelion are, respectively:

v=SQRT[GM( (2/r_p) -(1/a) )]

v=SQRT[GM( (2/r_a) - (1/a) )]

where M is mass of sun, r_a & r_p are distances from sun at aphelion and perihelion , and a is length of semi major axis.

How do you derive them? I am having trouble seeing where they come from, and a quick Google turns up NOTHING on them unfortunately.

ANy help?

v=SQRT[GM( (2/r_p) -(1/a) )]

v=SQRT[GM( (2/r_a) - (1/a) )]

where M is mass of sun, r_a & r_p are distances from sun at aphelion and perihelion , and a is length of semi major axis.

How do you derive them? I am having trouble seeing where they come from, and a quick Google turns up NOTHING on them unfortunately.

ANy help?