Calculating Frictional Force on a Roller Coaster: Solving for Final Velocity

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To calculate the final velocity of a roller coaster descending a hill with friction, one must consider the forces acting on it, including friction and gravity. The coefficient of friction and the angle of the hill are crucial for determining the frictional force. While mass is typically needed for calculations, in this case, it can be treated as an unknown that cancels out in the equations. The discussion emphasizes the importance of breaking down the problem into components and using work-energy principles. Ultimately, the participant successfully solved the problem with the guidance received.
Claire
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Homework Statement


Ok so there was a question on a physics quiz I did that I have no idea how to answer. There was a roller coaster going down a hill with an initial velocity of 1.67m/s. The hill is 60m long and had an angle of 40 degrees. There is a coefficient of friction of 0.100 with the roller coaster. We had to find the final velocity

Homework Equations


Ff=uFn
F=ma
d=volt + 1/2at2

The Attempt at a Solution


I honestly had no idea what to do for this question. I assume it had something to do with the x and y components of velocity, but I feel like you need mass or acceleration to answer this question and I don't know how to relate velocity to friction.
 
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Can you post your free body diagram please. By the way, welcome to Physics Forums.
 
Oh, and please show your x and y axes.
 
Claire said:
something to do with the x and y components of velocity
Not really.
Claire said:
you need mass
When a problem like this does not provide mass, either as a definite value or as an unknown allowed in the answer, it is a fair bet that it does not matter what the mass is. Just create an unknown, m, for it and expect it to cancel out later.
Claire said:
or acceleration
It can be done that way, but you do not need to find the acceleration.
Find the forces, then think about work done.
 
Thank you to everyone who offered to help, I figured out the answer!
 
The book claims the answer is that all the magnitudes are the same because "the gravitational force on the penguin is the same". I'm having trouble understanding this. I thought the buoyant force was equal to the weight of the fluid displaced. Weight depends on mass which depends on density. Therefore, due to the differing densities the buoyant force will be different in each case? Is this incorrect?

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