Calculating Speed of Roller Coaster Car at Top of Loop-the-Loop

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Homework Help Overview

The discussion revolves around calculating the speed of a roller coaster car at the top of a loop-the-loop, specifically focusing on the forces acting on the car, including gravitational and normal forces, in the context of circular motion.

Discussion Character

  • Conceptual clarification, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • Participants explore the relationship between normal force and gravitational force at the top of the loop, questioning whether the net force in the vertical direction is zero and how centripetal force is defined in this scenario.

Discussion Status

Several participants are engaged in clarifying the forces acting on the roller coaster car, with some suggesting that the centripetal force must equal the sum of the gravitational force and normal force. There is an ongoing exploration of the implications of these forces on the net force and the car's speed.

Contextual Notes

Participants note the lack of specific variables such as mass and speed in the problem statement, which raises questions about the solvability of the problem and the assumptions being made regarding the forces involved.

ceday
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Homework Statement


The normal force equals the magnitude of the gravitational force as a roller coaster car crosses the top of a 60m diameter loop-the-loop.



Homework Equations


What is the car's speed at the top?


The Attempt at a Solution


hello, this problem doesn't give much information
would normal force be pointing down?

so Fnet= ma=mv^2/r but its doesn't give those variables

can anyone help?
thanks :)
 
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Don't you have all you need?

Draw a diagram.

m*g down and mv2/r up

But it says the Normal force is still m*g

If the net force must be m*g and you have m*g acting down against the centripetal force, what must the centripetal force be?
 
Is the net force in the y direction zero?

does the centripetal force = 2mg since normal and gravity both point downward?

im lost since this coaster is upside down
 
ceday said:
Is the net force in the y direction zero?

does the centripetal force = 2mg since normal and gravity both point downward?

im lost since this coaster is upside down

Not lost at all.

The centripetal force is 2*m*g.
 
so would net force in the y direction = zero?

if it is zero, i don't think it would be solvable because we don't know the mass

wouldnt it be 0=mv2/r
 
ok, i got the answer but i used the net force=2mg
i still don't understand why this is so
 
ceday said:
ok, i got the answer but i used the net force=2mg
i still don't understand why this is so

FNormal = ∑ F = Fcentrip - Fgravity

m*g = m*v2/r - m*g

2*m*g = m*v2/r
 

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