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Constant Breaking force for roller coaster

  1. May 27, 2014 #1
    I really don't understand this:

    Consider a frictionless, 12000-kg roller coaster that starts at rest at the top of a hill, point A, 95 m high. It goes all the way the 75 degree steep hill and coasts horizontally (for an unspecified distance) before reaching point B (0 m high). The entire ride lasts 10 seconds and breaks engage with a constant force during last 4 seconds. Calculate:

    a) the constant breaking force that must be applied to bring the roller coaster to a stop at point B.

    b) the work being done by breaks to bring the roller coaster to a stop at point B.


    I don't understand the question at all. The wording is weird. How would I start this? I have no clue what so ever.
     
  2. jcsd
  3. May 27, 2014 #2

    SammyS

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    Except for the misspelling of "brakes" and "braking", the description is quite clear.

    Do you know about:

    Conservation of Energy?

    Work?

    Newton's 2nd law?

    Kinematic equations?

    etc.
     
  4. May 27, 2014 #3
    Yup, I know those equations.

    I know that first we're going to figure out the distance down the slope. I used the sin law to figure out the length. Then I'm going to use the first kinematic equations (V2=V1+AxT , where V2 equals final velocity, V1 equals initial velocity, A equals acceleration, T equals time). Once I solve for acceleration, I would then use the Force = Mass x Acceleration formula to solve for the force required for the break.

    Would I be able to find the correct answer using this method?

    Thank you so much for your help!
     
  5. May 27, 2014 #4

    SammyS

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    You should be able to use Conservation of Energy to find the speed of the roller coaster at the bottom of the hill, before braking.
     
  6. May 27, 2014 #5
    How would I use the Conservation of Energy formula?

    If the equation is ET=1/2(mass)(Velocity squared) + (mass)(gravity)(height)

    Would I assume height to be zero? Or would it be 95m?

    EDIT: I know I would isolate Velocity Squared.
     
    Last edited: May 27, 2014
  7. May 27, 2014 #6
    Please someone! I need urgent help. I need to know how to do this before tomorrow. I am begging.
     
  8. May 28, 2014 #7

    tms

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    You look at the total energy at the top and at the bottom of the slope.
     
  9. May 28, 2014 #8

    SammyS

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    There is a starting height and an ending height.

    ...
     
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