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etothey
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Homework Statement
An 840kg roller-coaster car is launched from a giant spring of constant k=31kN/m into a frictionless loop-the-loop track of radius 6.2m. What is the minimum amount that the spring must be compressed if the car is to stay on the track?
Homework Equations
Wspring=0.5kx^2
Wkinetic = 0.5mv^2
Wpotential = mgh
The Attempt at a Solution
I have an attempt but it is not correct and I would be thankful if someone could tell me why.
0.5kx^2=0.5mv^2=mgh
Thus x=(mgh*2/k)^0.5
x=(840*9.8*12.4*2/31000)^0.5
x=2.57m.
The answer should be 2.87m.
Thankful for any help.