What is the distance needed for a rocket to reach a velocity of 0 on Planet X?

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Discussion Overview

The discussion revolves around the concept of escape velocity on Planet X and the conditions under which a rocket can achieve a velocity of 0. Participants explore the implications of escape velocity, the nature of the question posed, and the assumptions involved in determining the necessary distance for the rocket.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant suggests that the escape velocity is the speed needed for a rocket to never fall back down, questioning how far it must be when its velocity is 0.
  • Another participant argues that understanding the implications of escape velocity is key, implying that there may not be a straightforward solution.
  • Some participants express skepticism about the question, suggesting it may be a trick question due to the ambiguous nature of speed and the rocket's state.
  • A participant mentions a hint from their professor to call the position Xf, indicating that the answer might be deceptively simple.
  • One participant claims that according to the escape velocity equation, achieving a velocity of 0 would require an infinite distance from the center of Planet X, while also considering the possibility of the rocket being at the planet's center.

Areas of Agreement / Disagreement

Participants do not reach a consensus on whether the question is a trick question or a common misunderstanding of escape velocity. Multiple competing views remain regarding the interpretation of the problem and the implications of escape velocity.

Contextual Notes

There are unresolved assumptions regarding the definitions of speed and position in the context of escape velocity, as well as the implications of the rocket's thrust capabilities.

scoop91
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The escape velocity on Planet X is the speed the rocket needs in order to never fall back down again in a universe in which X is the only object. In order for the rocket to not fall back down, its velocity to never become negative, how far away does the rocket have to be when the velocity is 0?

What are the steps to solving a problem such as this one?
 
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Welcome to PF!

There's nothing to solve there, it is just a matter of understanding the implications of escape velocity. I'd start by reading the wiki on it...
 
So all in all, it ends up being a trick question? Lol
 
scoop91 said:
So all in all, it ends up being a trick question? Lol

It depends if the speed is the rocket or the rocket is the speed or some weird quantum superposition of speed/rocket states.
 
bp_psy said:
It depends if the speed is the rocket or the rocket is the speed or some weird quantum superposition of speed/rocket states.

Our prof gave us a hint and told us to call the position Xf. He indicated that the answer was right under our noses.

Which led me to believe that there was some deception involved.
 
scoop91 said:
So all in all, it ends up being a trick question? Lol
I don't see it as a trick question, no. This is a common question people have/don't understand regarding escape velocity.

Did you find the answer?
 
According to the escape velocity equation, the distance from the centre of Planet X would need to be infinite to achieve a velocity of 0. It could always reverse it's thrust to achieve a velocity of 0, but the question says it can't. OR considering the definition of escape velocity and the common misconceptions, the answer is probably the rocket would have to be inside the planets centre, where r = 0.
 
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