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Homework Help: A simple confusion: Showing projectile is launched horizontally

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  1. Jan 12, 2017 #1
    • Member warned to use the homework template for posts in the homework sections of PF.
    The equation of trajectory of ball B is y = -0.05x^2 where y is vertical displacement and x is horizontal. Prove that the ball is projected horizontally


    For this, the mark scheme says
    x tan a = 0 so a =0
    Since the angle between ball and surface is 0 the object is projected horizontally.
    I can't work out how is x tan a = 0
     
    Last edited: Jan 12, 2017
  2. jcsd
  3. Jan 12, 2017 #2

    mfb

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    Staff: Mentor

    The problem statement got lost somehow.
     
  4. Jan 12, 2017 #3
    Please check again
     
  5. Jan 12, 2017 #4

    mfb

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    Staff: Mentor

    I don't see where the x would come from.

    tan a is the derivative of your function at x=0. The derivative is 0, therefore tan a = 0.
     
  6. Jan 12, 2017 #5
    How do you know the derivative is 0?
     
  7. Jan 12, 2017 #6
    Got it thanks
     
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