Roller Coaster Problem with KE and PE

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Homework Help Overview

The discussion revolves around a roller coaster problem involving kinetic energy (KE) and potential energy (PE). Participants are examining the relationships between these forms of energy at different points along the coaster's path, particularly focusing on parts D and E of the problem statement.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • The original poster attempts to apply the conservation of mechanical energy principle, questioning the ambiguity in the problem's language and how to proceed without knowing both velocities. Others suggest using the work-energy principle and calculating potential energy at various points.

Discussion Status

The discussion is active, with participants exploring different interpretations of the problem and offering guidance on the application of energy principles. There is no explicit consensus yet, but various approaches are being considered.

Contextual Notes

Participants note the ambiguity in the problem statement and the challenge of not having all necessary information, such as the velocities at specific points. The original poster expresses uncertainty about the simplicity of the calculations involved.

chris61986
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Homework Statement



https://dl.dropbox.com/u/92857534/physicsproblem.png

Note: Solving for part D and E

Homework Equations



Unsure. language in the problem seems ambiguous.
Perhaps (KE + PE)b = (KE + PE)a

The Attempt at a Solution



So I think it's done this way.

From A to B and B to C, the equation would look this way:
PEb + KEb = KEa + PEa
PEa = 0, move KEb to right side, left with:
PEb = KEa - KEb
so WGH = 1/2mv'^2 - 1/2mv^2

Am I going the right way about this? If so, where do I go from here when I don't know both velocities?
Also, for parts A, B, and C, it's simply W = mgΔh, correct? I'm not used to things being easy :P
 
Last edited by a moderator:
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Work energy rule says that the increase in kinetic energy of a body is equal to work done on it.
 
Do you think you could be a little less cryptic?
 
Work done by gravity is equal to the increase in kinetic energy of the car. The same is the loss in potential energy. W = mgΔh is correct.
In second part I think potential energy is to be calculated at different points.
 

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