# What is the answer to the Hershey Park Physics packet for the Sidewinder? http://www.hersheypark.com/groups/pdf/physics.pdf (Only one question please)

crmhaske | College Teacher | (Level 3) Associate Educator

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In a frictionless system, the prediction should be that the kinetic energy at the bottom of the hill will be equal to the potential energy at the top of the hill; however, it isn't a frictionless system. Energy is lost to friction (with the rails, with the air, etc.) between the top and bottom of the hill; therefore, some of the energy will be lost. Consequently, the most accurate prediction is b) About 70% of the `E_p` at the top.

As we do not have the lab data, we are unable to make specific calculations. I will make up some data to fill in the data we are missing.

We are given that:

m = 8260 kg
h = 35.5 m
L = 18.3 m
g = 9.8 m/s^2

`E_p=mgDeltah=(8260)(9.8)(35.5-0)= 2,873,654 J`

Let's say that it took t= 0.75s for the full length of the train to pass a point at the bottom of the hill; therefore,

`v = 18.3/0.75 = 24.4m/s`

`E_k=1/2mv^2=1/2(8260)(24.4)^2=2,458,836.8 J`

Therefore, the percentage of `E_p` that is equal to `E_k` at the bottom of the hill is:

`%=100E_k/E_p=100(2458836.8/2873654)=85.6%`

It is reasonable to expect that 14.4% of the potential energy was lost to friction.

The second question cannot be answered without having been on the ride.

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