Comets travel around the sun in elliptical orbits with large eccentricities. If
ID: 1518829 • Letter: C
Question
Comets travel around the sun in elliptical orbits with large eccentricities. If a comet has speed 2.4×104 m/s when at a distance of 2.1×1011 m from the center of the sun, what is its speed when at a distance of 5.1×1010 m . Express your answer using two significant figures. Use this link in order to make sure you follow the methodology and get the correct answer: https://www.chegg.com/homework-help/questions-and-answers/comets-travel-around-sun-elliptical-orbits-large-eccentricities-comet-speed-24-104-m-s-dis-q9704589
The answer is NOT 6.23 x 104 m/s, btw.
Explanation / Answer
To resolve this problem we will use the first and second laws of Kepler
L = r x p bold indicate the vectors
L = r m v
where speed is perpendicular to the radius vector, as the comet- sol system is isolated momentum is preserved
Li = Lf
r1 m v1 = r2 m v2
Calculate
v2 = v1 r1/r2
v2 = 2.4 104 2.1 1011/ 5.1 1010
v2 = 9.88 104 m/s
Result 9.9 104m/s