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How is lift force proportional to speed up?

  1. Mar 21, 2013 #1
    i know that if i have a greater lift force, there will be a greater speed upwards, but i don't know to calculate a speed of something upwards. is this even possible to calculate? if it's not, can you give a calculation example??
  2. jcsd
  3. Mar 21, 2013 #2


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    Work out the net force acting on the object in the vertical direction..

    Net Force = Lift - Weight

    Then apply Newton..

    Net Force = mass * acceleration

    If lift = weight then there is no net force acting on the object so it's vertical velocity will be constant (eg acceleration = 0).
  4. Mar 21, 2013 #3
    is weight the atmospheric pressure or how much the body weighs? just want to make sure.
  5. Mar 21, 2013 #4


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    By definition, lift is perpendicular to the direction of travel (with respect to the air), so it only changes direction, not speed. If a plane is in a steady vertical climb at some constant angle θ above horitzontal, with a vertical speed component of speed x sin(θ), then there needs to be enough thrust and lift so that the vertical components of thrust and lift equal the weight of the aircraft:

    thrust x sin(θ) + lift x cos(θ) = weight.
  6. Mar 21, 2013 #5
    okay then, thank you all!
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