Impossible Roller Coaster question (for me anyway)

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Homework Help Overview

The discussion revolves around a physics problem related to energy conservation in a roller coaster scenario. Participants are exploring the application of energy equations to analyze the motion of a cart on a track, particularly focusing on the relationship between kinetic and gravitational potential energy.

Discussion Character

  • Exploratory, Assumption checking, Conceptual clarification

Approaches and Questions Raised

  • Participants discuss the necessity of energy equations and question how to derive total mechanical energy without knowing the mass of the cart. There are attempts to express the conservation of energy and concerns about the sufficiency of given information.

Discussion Status

The discussion is ongoing, with participants providing guidance on how to approach the problem. Some have suggested writing equations to express total energy, while others are still grappling with the implications of missing information. There is a mix of understanding and confusion regarding the relationship between energy components.

Contextual Notes

Participants note the challenge of solving the problem with limited information, specifically the mass of the cart and how it affects calculations. The original poster expresses frustration with the complexity of the topic.

scolaiw
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Question in this link (includes diagram): http://b.imagehost.org/view/0431/photo"

I am assuming it require Energy equations

The attempt at solution = Fail

Please HELP!
 
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scolaiw said:
I am assuming it require Energy equations
Definitely.

The attempt at solution = Fail
For some reason, you set KE = GPE. Instead, consider the total energy at any point. That total energy doesn't change. Write an equation expressing that fact.
 
I still don't get it... How can you do so, without knowing the mass of "cart"? Where does all the velocities factor into this?
 
How come no one replies...?
 
scolaiw said:
I still don't get it... How can you do so, without knowing the mass of "cart"? Where does all the velocities factor into this?
Call the mass of the cart 'm'. It doesn't matter and will drop out of any calculation.

Did you write an expression for the total mechanical energy of the cart?
 
Yeah that's what I don't get, how can you get the total mechanical energy from so little information?

Thanks so far btw.
 
scolaiw said:
Yeah that's what I don't get, how can you get the total mechanical energy from so little information?
You don't need the actual numerical value for the total energy. (You don't have the mass, afterall.) All you need to find is the height of point Y and you are given all the information you need to do that.

Compare the total energy at point X to the total energy at point Y.
 
Ok I've exhausted just about all of my effort and still not getting it. Physics is hard for 17 year old :P.

Can you please tell me the first line of the equation?
 
I am thinking 0.5mv^2 + mgh = 0.5mv^2 + mgh and solving for second h.
 
  • #10
scolaiw said:
I am thinking 0.5mv^2 + mgh = 0.5mv^2 + mgh and solving for second h.
Exactly!
 

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