Escape velocity earth confusion

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Discussion Overview

The discussion revolves around the concept of escape velocity on Earth, particularly addressing confusion regarding its definition and implications in relation to the Earth's rotation and atmospheric retention. Participants explore theoretical aspects, practical implications, and the relationship between escape velocity and the velocity of the Earth.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions how the atmosphere remains bound to Earth if escape velocity is 11 km/s and the Earth's velocity is 30 km/s, suggesting a misunderstanding of the reference frame for escape velocity.
  • Another participant clarifies that escape velocity is indeed relative to Earth, noting that only a small fraction of atmospheric molecules can achieve this velocity.
  • There is a query about the relationship between escape velocity and the direction of projectile motion, with participants discussing the implications of launching projectiles in the direction of Earth's rotation.
  • A later reply emphasizes that while escape velocity is relative to Earth, the initial speed of a projectile launched eastward at the equator can reduce the required fuel to achieve escape velocity.

Areas of Agreement / Disagreement

Participants express differing views on the implications of escape velocity in relation to Earth's rotation and the behavior of projectiles. The discussion does not reach a consensus, as multiple perspectives on the relationship between escape velocity and atmospheric retention are presented.

Contextual Notes

Some assumptions regarding the definitions of escape velocity and the effects of Earth's rotation on projectile motion remain unresolved. The discussion highlights the complexity of these concepts without providing definitive answers.

AakashPandita
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If escape velocity on Earth is 11 km/s and velocity of Earth is 30 km/s how is that the atmosphere doesn't escape the pull of earth.
Is the escape velocity with reference to Earth ? I don't think so because when finding the formula we add kinetic and potential energy and then equate to zero. If it is not then doesn't everything on Earth has velocity greater than escape velocity...
Please help me out.
 
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The escape velocity on Earth is relative to the earth. In the outer fringes of the atmosphere, a very tiny percentage of molecules will randomly end up with >= escape velocity. Escape velocity from the solar system, is relative to the Sun (with some effect from orbiting planets). There are a few satellites that have exceeded escape velocity from the solar system. A list of them from wiki:

http://en.wikipedia.org/wiki/List_of_artificial_objects_escaping_from_the_Solar_System
 
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If the escape velocity is relative to Earth then why is it that( i read in my book) that projectiles are projected in the direction of rotation of Earth ?
 
AakashPandita said:
If the escape velocity is relative to Earth then why is it that( i read in my book) that projectiles are projected in the direction of rotation of Earth ?
It's relative to the Earth centered non-rotating frame.
 
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AakashPandita said:
If escape velocity on Earth is 11 km/s and velocity of Earth is 30 km/s
At the equator, the surface speed of the Earth relative to it's center of mass is about 0.464 km/s. As posted by A.T., the escape velocity from the Earth is not affected by the Earth rotation, but by launching a rocket to the east at the equator the rocket would start with 0.464 km/s speed relative to the center of mass of the earth, reducing the fuel it would need to reach orbital or escape velocity speeds.
 
Thanks. It makes sense to me now,
 

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