Help with Escape Velocity Problem

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Discussion Overview

The discussion revolves around the concept of escape velocity, specifically in the context of escaping the gravitational influences of both the Moon and Earth. Participants explore the calculations involved in determining the approximate escape speed needed to leave the gravitational pull of both celestial bodies.

Discussion Character

  • Exploratory
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant states the formula for escape velocity as v^2 = 2GM/r and questions how to calculate the escape speed needed to escape both the Moon and Earth's gravity.
  • Another participant suggests that the escape velocities can be added together, noting that the Moon's escape velocity is relatively small.
  • A different participant expresses uncertainty about the addition of escape velocities, proposing that an object escaping from the Moon would need to travel slightly slower than Earth's escape velocity due to the increased distance from Earth.
  • One participant interprets the question as asking for the escape velocity from the Earth-Moon system, suggesting that the masses of both bodies should be combined for the calculation.
  • A participant clarifies the problem statement, emphasizing the need to find the escape speed specifically from the Moon while considering the gravitational effects of both bodies.
  • Another participant agrees with the idea of treating the Moon and Earth as a single object for a first approximation, suggesting that their escape velocities could be added.

Areas of Agreement / Disagreement

Participants express differing views on whether to add the escape velocities directly or to consider the gravitational influences of both bodies in a more complex manner. There is no consensus on the correct approach to calculating the escape speed.

Contextual Notes

Participants highlight assumptions regarding the negligible effect of the Moon's escape velocity and the interpretation of the problem statement, which may affect the calculations. The discussion does not resolve these assumptions or clarify the mathematical steps involved.

Who May Find This Useful

This discussion may be of interest to individuals studying gravitational physics, celestial mechanics, or those seeking to understand the concept of escape velocity in multi-body systems.

CaptainEvil
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I know that escape velocity is given by v^2 = 2GM/r

My question is what is the approximate escape speed needed to completely escape the moon & Earth's gravity.

Is it the sum of their individual Escape velocities? or is it one equation, with the radius' added and masses added?

Thanks
 
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I would add the escape velocities, the value for the moon is pretty small anyway
 
Yea I was thinking that something (i.e moons EV) would be negligable since the question asked for the approximate value. But are you sure of that? Wouldn't it make sense astronomically - for something to escape moon's and Earth's gravity - that's on the moon, to have to travel slightly slower than Earth's EV since now we are much farther away?
 
I read it to mean at a great distance from both what's the escape velocity, ie. of the earth-moon system, in which case the Earth and moon's masses add so you can approx add their escape Vs
 
The exact wording of my problem is as follows:

"assuming one wished to escape completely from both the moon and Earth's gravity, what would the approximate escape speed be from the moon?"
 
Thats why I would regard it as a single object - and so for a first approximation add the escape Vs
 

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