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Homework Help: Frictionless Slide (mastering Physics)

  1. Feb 2, 2009 #1
    1. The problem statement, all variables and given/known data
    A child slides down a frictionless 3.1 -long playground slide tilted upward at an angle of 37. At the end of the slide, there is an additional section that curves so that the child is launched off the end of the slide horizontally.

    Part A
    How fast is the child moving at the bottom of the slide?

    Part B
    If the end of the slide is 0.34 above the ground, how far from the end does she land?

    2. Relevant equations


    3. The attempt at a solution
    I think i have to find the total time the child spends on the slide before i can find her velocity im just not sure on how to go about doing that.
  2. jcsd
  3. Feb 2, 2009 #2


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    You need to find her velocity at the bottom of the incline.

    First you need to determine her acceleration down the slide.

    That can be determined by the angle with respect to gravity.

    With that acceleration - taken over the distance you can determine the velocity, which when she exits the slide will be all horizontal.

    Once you figure the time for her to fall .34 m after exiting, simply multiply her horizontal velocity and you will have where she lands away from the end of the slide. Horizontal velocity * time to fall is her distance.
  4. Feb 2, 2009 #3
    That can be determined by the angle with respect to gravity

    How do i know when to use sin cos or tan, and what one would i use here?
  5. Feb 2, 2009 #4


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    Resolve gravity into components normal to the incline and || along the incline.

    When you put in θ in your drawing, the side opposite your angle will be sine and the side adjacent to your θ will be cosine.
  6. Feb 2, 2009 #5
    thanks for the speedy reply, i will work on this for a bit now and see what i come up with
  7. Feb 2, 2009 #6
    ok for the acceleration i took the cos(37)*9.8 and came up with 7.82, is this even close to what i need to be doing?
  8. Feb 2, 2009 #7
    ok obvisouly im doing something wrong here, does anyone have a list of formulas for projectile motion. I dont seem to have any in the text book, and mastering physics is just giving me questions, no formulas.
  9. Feb 2, 2009 #8


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  10. Feb 2, 2009 #9
    ya i tried both sin and cos and timesed them by the gravity, and then i divided it by the length and part a was still wrong?
  11. Feb 2, 2009 #10
    "Frictionless" cries out for using conservation of energy to determine
    the final speed.

    mgh = (1/2)mv^2
  12. Feb 2, 2009 #11


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    True, but I gather the lesson is kinematics. One of the kinematic equations at the link provided is based on just this very conservation of energy, but I gather that ground has not yet been covered.
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