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Projectile Question

  1. Sep 16, 2008 #1
    A car is moving with constant velocity along a slope as shown in the figure. The magnitude of the velocity is 10m/s. Find the position of point A where the car hits the ground.

    Angle = 20 degree
    Height = 20m


    [​IMG]


    I have freaking no idea form where to start. Please help asap
     
  2. jcsd
  3. Sep 16, 2008 #2

    danago

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    What is the initial velocity in the vertical and horizontal directions?
     
  4. Sep 16, 2008 #3
    i think

    Vy = 10sin20degree

    Vx = 10cos20degree
     
  5. Sep 16, 2008 #4

    danago

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    Alright, now how can you determine how long before it hits the ground?
     
  6. Sep 16, 2008 #5
    y = vi * t + .5at*t

    20 = 3.4t - 5t*t
     
  7. Sep 16, 2008 #6

    danago

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    You need to be careful of your signs. You have acceleration as negative there, but you have both displacement and velocity as positive, even though they are in the same direction as acceleration here. If you try to solve that you will get complex solutions.
     
  8. Sep 16, 2008 #7
    so is it like

    -20 = -3.4t - 5t*t
     
  9. Sep 16, 2008 #8
    Is the positive y direction in your coordinate system pointing downward?
     
  10. Sep 16, 2008 #9

    danago

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    Thats better.
     
  11. Sep 16, 2008 #10
    then I just multiply t by Vx to get the ans

    thx a lot 4 the help
     
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