Does a Rocket's Potential Energy Increase as it Accelerates Away from Earth?

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Discussion Overview

The discussion revolves around the relationship between a rocket's potential energy (PE) and its acceleration as it moves away from Earth. Participants explore the concepts of work, kinetic energy (KE), and the forces acting on the rocket, including gravity and engine thrust.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions whether the potential energy of a rocket increases as it accelerates away from Earth, suggesting that if work done (W) equals the change in kinetic energy (dKE), then all work is converted to KE and not PE.
  • Another participant notes that there are two forces acting on the rocket: the engine thrust and gravity, implying that work done by gravity contributes to potential energy.
  • A participant asserts that the work done (W) is equal to the change in kinetic energy plus the change in potential energy (W = dKE + dPE), indicating that both forms of energy are involved.
  • Further clarification is provided that if considering only the work done by non-conservative forces (engine force), then W = ΔKE + ΔPE, while gravity's effects are represented through gravitational potential energy.
  • There is a reiteration of the equation W(Net) = Sum(Fs) = dKE, with some participants agreeing that this holds true when including gravity as a force acting on the rocket.

Areas of Agreement / Disagreement

Participants express differing views on how work, kinetic energy, and potential energy interact in the context of a rocket's motion. There is no consensus on the relationship between these quantities, and the discussion remains unresolved regarding the specifics of how potential energy changes with acceleration.

Contextual Notes

Some assumptions about the forces acting on the rocket and the definitions of work and energy are not fully explored, leading to potential ambiguities in the discussion.

pkc111
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Can someone please explain to me whether the potential energy of a rocket increases as it accelerates and moves further from Earth ?

My immediate answer is yes, but if W=dKE, then all of the work is being converted into KE and not PE ??

Thanks very much
 
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pkc111 said:
Can someone please explain to me whether the potential energy of a rocket increases as it accelerates and moves further from Earth ?

My immediate answer is yes, but if W=dKE, then all of the work is being converted into KE and not PE ??

Hi pkc111 :smile:

there are two forces on the rocket … the engines, and gravity.

work done by gravity (or any other conservative force) is just another name for PE :wink:
 
Thanks Tiny Tim
 
So if there are 2 forces acting on the rocket, how does W=dKE?
 
pkc111 said:
So if there are 2 forces acting on the rocket, how does W=dKE?
If you include the work done by all forces on the rocket including gravity, then W = ΔKE. But since gravity is a conservative force we usually represent its effects by introducing a gravitational PE. In that case, if we just consider the work done by non-conservative forces (the "engine force" only, not gravity, which is already included in PE), then W = ΔKE + ΔPE.
 
So

W(Net) = Sum(Fs)= dKE


right?
 
pkc111 said:
So

W(Net) = Sum(Fs)= dKE


right?
Yes, if you include gravity as a force acting on the rocket. (No PE term.)
 
woohoo!
thank you all very much
 

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