Finding Escape Velocity from a Gravitational Potential Energy Surface

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Homework Help Overview

The discussion revolves around finding an expression for escape velocity from a gravitational potential energy perspective, specifically considering an object at the surface of a celestial body. The subject area includes gravitational potential energy and escape velocity concepts.

Discussion Character

  • Exploratory, Assumption checking, Conceptual clarification

Approaches and Questions Raised

  • Participants discuss the relationship between gravitational potential energy and kinetic energy, with one participant attempting to derive escape velocity using basic equations. Others question whether the computed velocity aligns with the concept of escape velocity and highlight assumptions about gravitational force constancy.

Discussion Status

The discussion is active, with participants providing insights and questioning the original poster's assumptions. Some guidance has been offered regarding the use of the work-energy theorem and the need to consider gravitational potential energy in a nonconstant field. Multiple interpretations of escape velocity are being explored.

Contextual Notes

There is an ongoing discussion about the assumptions made regarding gravitational force and the implications for the concept of escape velocity. The original poster's approach may not fully align with the standard definition of escape velocity in varying gravitational fields.

imy786
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Homework Statement



By considering the gravitational potential energy of an object at the surface , find an expression for the escape speed from the surface and determine its value.

Homework Equations



GPE= mgh

The Attempt at a Solution



KE= 1/2* m * v^2

GPE= mgh

GPE+ KE = 0

mgh = - 1/2 * m * v^2
gh= - 1/2 * v^2


v^2= -2gh

v= sqare root of (-2gh)

this is the escape velocity...
 
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You've computed velocity needed to reach a height h in a uniform gravitational field. Is that the same concept as 'escape velocity'?
 
You also appear to be assuming gravitational force is constant. If that were true, there would be no "escape velocity". It is impossible to "escape" a constant force!
 
Well if ur looking for escape velocity...it should be\sqrt{\frac{2GM}{R}}
 
thanks for the info...
so how shall i start off instead
 
you shud use the work energy theorem
 
Last edited:
You should change your expression for gravitational potential energy to one appropriate for a nonconstant field.
 
Remember that gravity is an "inverse square formula"!
 

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