- #1
Nghi
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Homework Statement
A particular comet has an elliptical orbit. When closest to the Sun (perihelion) it is at a distance of 8.823 x 10^10 m and moves with a speed of 54.6 km/s. The greatest distance between this comet and the Sun (aphelion) is 5.902 x 10^12 m.
Calculate its speed at aphelion.
Homework Equations
Initial angular momentum = final angular momentum, since Kepler's law states that equal area is swept out at equal times.
The Attempt at a Solution
Li = Lf
Iw = Iw
(mr^2)w = (mr^2)w
(mr^2)(v/r) = (mr^2)(v/r)
Simplifying it, I get the result:
rv = rv
Plugging in the numbers, I get the following answer:
(8.823e10 m)(54,600 m/s) = (5.902e12)(v)
v = 816.225 m/s
= 0.816225 km/s
That's not the right answer, though, and it bothers me like whoa. It's because my professor sent a mass email out yesterday, explaining how a similar problem on the homework had been wrong. So he posted this question up instead, and it's the exact same problem, only with different numbers. When I did the original problem, I got the right answer following this method. Now, it's wrong, and it's confusing me. Any ideas?