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Sir Isaac Newton Contest Question (Energy)

  1. Oct 26, 2009 #1
    Hey
    This problem has been stumping me for awhile and I just don't seem able to get it


    1. The problem statement, all variables and given/known data
    A space shuttle lands ona distant planet where the gravitiational acceleration is 2.0 (We don't know the local units of length and timem but they are consistent throughout this problem.) The shuttle coasts alond a level, frictionless plane with a speed of 6.0. It then coasts up a frictionless ram of height 5.0 and angle 30 degrees. After a brief ballistic flight, it lands a distance S from the ramp. Solve for S in local units of length. Assume the shuttle is small compared to the local length unit and that all atmospheric effects are negligible.


    2. Relevant equations
    I used the equation
    Eg=mgy
    Ek=0.5mv^2



    3. The attempt at a solution
    first befor it hits the ramp
    mv^2/2 = 18m (m is not meters)
    on the ramp mgh would be introduced so
    mgh+mv^2=?
    And this is where I got lost
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Oct 26, 2009 #2

    Delphi51

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    I like to write out the whole thought before resorting to numbers!
    I'd say energy before ramp = energy after ramp
    KE = KE + PE
    ½mv² = ½mv² + mgh
    Hope that is a start for you. Remember the v on the left is the 6 you know and the v on the right is the end of ramp speed you are looking for.
     
  4. Oct 26, 2009 #3
    I'll try to do this but i'm not sure if I can get the right answer (I'm taking intro mechanics). So do you have the answer for me to check?
     
  5. Oct 26, 2009 #4

    Delphi51

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    You go first, ahmadmz!
     
  6. Oct 26, 2009 #5
    Ok I did it something like this :

    Like you said Energy has to be same, so
    Bottom of ramp, (call it point 1) K1 = (mv1)/2 and U1 = 0
    Top most part of ramp , (point 2) K2 = (mv2)/2 + 5*m*2 (This 2 is the "g" here).
    Equating K1 + U1 = K2 + U2 we can solve for v2 = 4
    Then maybe we can use the kinematic equations for constant acceleration to find the S?

    Or is there a way to solve this using energy methods only? We are doing this right now in class so I need more experience :)
     
  7. Oct 26, 2009 #6

    Delphi51

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    The 4 looks good. The rest of it is a pretty standard 2D projectile motion question - just remember the end point is below the start point. You know the routine - write out your equations for both the horizontal and vertical parts.
     
  8. Oct 27, 2009 #7
    Actually what it sys in the back of the book is 12 units. All that realy needs to be done now is use a projectile motion equation and it should give me the answer.
     
    Last edited: Oct 27, 2009
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