# Comet on a parabolic orbit around the Sun

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1. May 26, 2015

### math 2015

1. The problem statement, all variables and given/known data
given: the speed at perihelion

What is comets full energy? What is its distance from Sun at perihelion?
How much time is the comet located inside Earth's orbit?

2. Relevant equations
parabolic orbit equation

3. The attempt at a solutin
wrongly calculated l

2. May 26, 2015

### theodoros.mihos

$$r(\theta) = \frac{L^2}{GMm^3}\,\frac{1}{1+\epsilon\,\cos{\theta}}$$
L is constant, so the same for every $\theta$. Take an easy value.

3. May 26, 2015

### Staff: Mentor

You're first asked about the "full energy" of the of the comet's orbit. Presumably that's the mechanical energy. What is the expression for the specific mechanical energy (ξ) of an orbit? What is its value for any parabolic orbit?

In order to answer the part about the time spent within the Earth's orbit you will need some hard data. Are you given an actual value for the speed at perihelion?

4. May 26, 2015

### math 2015

94 km/s

5. May 26, 2015

### Staff: Mentor

Okay, now you'll have to show some details of your efforts so far to answer the given problem.

6. May 27, 2015

### Staff: Mentor

@math 2015 I'm closing this thread since you haven't shown any effort. If you wish to continue, contact me or begin a new thread showing your attempt in detail.