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Projectile motion

  1. Sep 23, 2009 #1
    1. The problem statement, all variables and given/known data
    a track is inclined in such way that the velocity of the metal ball is 60 cm/s at 25 degree below the horizontal. mathematically determine the total x displacement of the metal ball.

    weight of ball: 65grams
    height from floor to the end of the track: 76.15cm
    velocity of the ball is 60.cm/s at 25 degree

    2. Relevant equations
    [tex]\Delta[/tex]y =Vo*t - .5 1/2gt^2
    Vx = Vox + .5at^2

    3. The attempt at a solution
    I used the first equation to find time.
    -76.15 = .5*-9.8t^2
    t=.394s
    deltaX = .6m/s*cos(-25).3942 + .5(-9.8).3942^2
    i got delta X to be -54.7cm

    is it suppose to be negative?

    Could someone help me set this up right?
     
    Last edited: Sep 23, 2009
  2. jcsd
  3. Sep 23, 2009 #2

    rl.bhat

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    Hi goodz, welcome to Pf.
    In the y direction the initial velocity is not equal to zero.
    And in the x direction there is no acceleration.
     
  4. Sep 23, 2009 #3
    I think i got it.
    first i needed to get the velocity using v^2 = VoSin(-25)^2 - 2(-9.8).7615
    v = 3.87m/s
    then to get time,
    3.87 = .6Sin(-25)-(-9.8)t
    t=.4207
     
    Last edited: Sep 23, 2009
  5. Sep 23, 2009 #4

    rl.bhat

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    If you take down as negative v, vi and g are all negative. So check the value of t.
     
  6. Sep 23, 2009 #5
    are you saying .6m should be negative?
     
  7. Sep 23, 2009 #6

    rl.bhat

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    Allare positive or negative.
    The equation should be
    v = vosin(25) + gt.
     
  8. Sep 23, 2009 #7
    3.87 = .6(sin25)+9.8t
    t=.369s

    x= voCos25t
    x=.6cos25(.369)
    x=.20m
     
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