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Help with Physics Problem?

  1. Dec 8, 2009 #1
    1.The problem statement, all variables and given/known data

    1. You want to toss the pebbles up to a friend's window such that the pebbles hit the window with only a horizontal component of velocity. The window is 8.00m above you and there is a 6.00m wide flowerbed between you and the wall of the house. A) How fast do you throw the pebble? B) How fast are the pebbles going when they hit your friend's window?

    2. Relative Equations
    2. X=Xo+Vxo*t Y=Yo+Vyot+.5at^2

    3. Attempt at the solution.
    3. I know that we have to solve for initial velocity and then final velocity with only the horizontal (x) component. What I did was use trig to get tan(theta)=8/6 to get theta=53degrees. From there I plugged the variables into the equations to get
    8=Vosin(theta)*t-.5*g*t^2 and 6=Vcos(theta)*t From here I'm not really sure what to do or even if I set up the equation right. Any help would be soooo appreciated!! Thank you.
  2. jcsd
  3. Dec 8, 2009 #2
    Image you are standing right below the window, and you want to throw the rock directly upward so that it *just* reaches the window at the top of its flight. The velocity at which you have to throw the pebble for this to happen will be the y-component of velocity in your situation. Since you don't have t, try using V2=Vo2+2*a*d to calculate this.

    Then once you know what the y-component of velocity is, you should be able to find the x-component easily.
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