How Does Eccentricity Influence Orbital Speed Ratios in Planetary Motion?

Therefore, the correct ratio is (1+e)/(1-e), which in this case is (1+0.006800)/(1-0.006800) = 1.01361. In summary, the ratio of orbital speed at perihelion to that at aphelion can be found by taking the ratio of the semimajor axis to the semiminor axis, which in this case is (1+e)/(1-e) where e is the eccentricity. For the given planet with an eccentricity of 0.006800 and a semimajor axis of 0.7233 AU, the ratio is 1.01361.
  • #1
sheepcountme
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Homework Statement


A planet has an eccentricity of 0.006800 and a semimajor axis of 0.7233 AU, find the ratio of ortibal speed at perihelion to that at aphelion.


Homework Equations



d=e x a
L=mvrsin[tex]\theta[/tex]

The Attempt at a Solution


I plugged in and solved for the distance between the foci (0.004918)
and then set the angular momentum constants equal to each other:
m v(p) rmin sin[tex]\theta[/tex]=m v(a) rmax sin[tex]\theta[/tex]
the masses and sin[tex]\theta[/tex] cancel out, so
v(p) x r min = v(a) x r max
and so the ratio is:
v(p) / v(a) = r max / r min

r max is the semimajor axis, and r min is the semimajor axis minus the d as found above:
So, it should be .7233/.718382 which gives me 1.00685, but this was incorrect according to my online homework, could you tell me what I did wrong?
 
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  • #2
The relation vp/va = ra/rp is correct, but ra and rp are the aphelion and perihelion distances, respectively, and are given by ra = a(1+e) and rp = a(1-e).
 

FAQ: How Does Eccentricity Influence Orbital Speed Ratios in Planetary Motion?

What is angular momentum?

Angular momentum is a physical quantity that describes the rotational motion of an object around an axis. It is a vector quantity, meaning it has both magnitude and direction.

How is angular momentum calculated?

The formula for calculating angular momentum is L = Iω, where L is the angular momentum, I is the moment of inertia, and ω is the angular velocity. Moment of inertia is a measure of an object's resistance to rotational motion and angular velocity is the rate of change of angular displacement.

How does angular momentum affect orbits?

Angular momentum plays a crucial role in determining the shape and stability of orbits. According to the law of conservation of angular momentum, in the absence of external torques, the angular momentum of an object in orbit remains constant. This means that as the object moves closer to the center of mass, its speed increases to maintain the same angular momentum.

What is the difference between angular momentum and linear momentum?

Angular momentum and linear momentum are both measures of an object's motion, but they describe different types of motion. Linear momentum is a measure of an object's motion in a straight line, while angular momentum is a measure of an object's rotational motion around an axis.

Can angular momentum be negative?

Yes, angular momentum can be negative. It depends on the direction of the vector quantity. If the direction of the angular momentum is opposite to the direction of the angular velocity, it will be negative. This can happen in cases where the object's angular velocity changes direction, such as in a retrograde orbit.

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