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Velocity to forces (Newtons)

  1. Oct 30, 2011 #1
    1. an aeroplane of mass 300 tonnes during ascent travels at a constant velocity of 100 m/s. its angle of ascent is 10° to the horizontal. the trust produced by engines is 9000kN. Determine
    i)the lift force acting on the wings
    ii) the resistance to motion

    i were trying to use f=ma, but the question didnt mention about the time, is it we need to convert 9000kN to acceleration in order to get time is second or can i get it from the question above, in other way i research via google with other website, some get F = 0N, is it possible?

    secondly, the resistance is it = lift force or is it a drag force

  2. jcsd
  3. Oct 30, 2011 #2


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    Homework Helper

    Welcome to PF, emperror.
    The plane is not accelerating, so both the vertical and horizontal forces must be zero. For the vertical forces, you have a component of thrust upward, lift upward and the weight downward. You also have a component of the drag (resistance to motion) downward. Looks like two unknowns there, so you will have to write a similar equation for the horizontal forces and solve the two as a system.
  4. Oct 31, 2011 #3
    u mean i have to find the vertical axis 1st before i can do the horizontal axis?
    and i can assume that the velocity with angle with 0N?

    thrust is it on horizontal or vertical? cause u said that the thrust is upward (y-axis), make me doubt on whether is it horizontal or vertical

    thank for ya reply
  5. Oct 31, 2011 #4


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    Note that thrust and drag are partly horizontal and partly vertical.
    You must use sine and cosine to get their horizontal and vertical components.
    The vertical component of thrust will be 9000 kN *sin(10).
    Recommend you start with the horizontal part; looks like it will be easy to solve for the drag.
    Last edited: Oct 31, 2011
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