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Homework Help: Motion at Constant Acceleration Question 2

  1. Jan 14, 2010 #1
    1. The problem statement, all variables and given/known data
    A light plane must reach a speed of 33 m/s for takeoff. How long a runway is needed if the (constant) acceleration is 3.0m/s^2?


    2. Relevant equations
    I looked at the Kinematics Equations and tried to re-arrange them to be able to find the distance with what I was given.


    3. The attempt at a solution
    I am not sure how to start it, this is always my problem I can't seem to figure out what formula to use.
     
  2. jcsd
  3. Jan 14, 2010 #2

    rock.freak667

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    You have a final velocity, an initial velocity (the plane should be at rest) and an acceleration. You want to find a displacement.

    Which of the kinematic equation contains those 4 quantities?
     
  4. Jan 14, 2010 #3
    vf^2 = Vi^2 +2ad.......?
     
  5. Jan 14, 2010 #4

    rock.freak667

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    So when you use that, what do you get for 'd'?
     
  6. Jan 14, 2010 #5
    v^2 = 0 * 2as
    where v is final velocity, a is acceleration and s is the distance
     
  7. Jan 14, 2010 #6
    I got 1.8 m/s and thats the right answer thanks so much for the help
     
  8. Jan 14, 2010 #7

    rock.freak667

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    you mean you got 1.8m. m/s are the units for velocity.
     
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