- #1
Gary Roach
- 20
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Homework Statement
Compute the semimajor axes "a" of Halley's Comet.
Given:
orbital eccentricity e = 0.9673
period P =76 days (2.39674E9 seconds)
Gravitational Constant G = 6.67428E-11
solar mass M = 1.9891E30 Kg.
Also used in equations are:
L = angular momentum of center of mass
[tex]\mu[/tex] = reduced mass
r = distance from focus to comet mass
b= semiminor axis of elipse.
Homework Equations
I used:
[tex]
\frac{dA}{dt} = \frac{L}{2\mu} = \frac{A}{P}
[/tex]
[tex] A=\pi a b [/tex]
[tex] b^2=a^2(1-e^2) [/tex]
[tex] L=\mu\sqrt{GMa(1-e^2)}[/tex] from text
The Attempt at a Solution
[tex] L=\frac{2\pi \mu a^2 (1-e^2)}{P} = \mu \sqrt{GMa(1-e^2}[/tex]
[tex] a = \sqrt[1/3]{\frac{GMP^2}{4\pi^2 (1-e^2)}} [/tex]
Unfortunately "a" turns out to be 6.6964E12 meters = 44.76 AU .
Since the data is for Halley's Comet, a should be 17.8 AU
Where did I go wrong