Use the following data to calculate the speed vp of comet Halley at perihelion. Comet Halley orbits the Sun with a period of 76 years and in 1986 had a distance of closest approach of 8.90×1010 m and an aphelion distance of 5.30×1012 m.(adsbygoogle = window.adsbygoogle || []).push({});

I'm stumped so far on this one. I'm assuming the closest approach distance is useless info thrown in there. I know I could use keplers law of periods to find what the perihelion distance is, and I know that angular momentum is constant, so I could find the velocity at aphelion if I knew vp, but I can't figure out how to get vp.

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# Homework Help: Gravity, Kepler's Laws

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