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Urgent physics problem

  1. Apr 19, 2008 #1
    1. The problem statement, all variables and given/known data
    A fully loaded Cessna-182 airplane of mass 1290kg has an engine failure when flying with an airspeed of 139 km/h at an altitude of 2710 m on a calm day. it then glides at a constant glide angle(which is the direction of flight below the horizontal) towards a safe landing at this constant speed of 139km/h experiencing a drag force of 1270 N that opposes the directin in which the plane is moving.
    i) Find the magnitude of:

    a) The glide angle
    5.75 degrees

    b) The lift force.
    12654.9 N

    c) The rate at which the loaded plane is losing gravitational potential energy[/B]

    ii) Suppose the pilot instead had managed to get the airplane engine started such that he was able to apply full throttle and the airplane climbed along a straight line angled above the horizontal so that it gained altitude at a steady rate of 5.61 m/s. Assuming he was again flying with an airspeed of 139km/h determine:

    i) the flight angle above the horizontal the plane is flying.

    3. The attempt at a solution

    I have already found the glide angle and lift force using F = mg cos(theta)
    The glide angle is 5.76 degrees
    The lift force is 12654.9 N
     
  2. jcsd
  3. Apr 19, 2008 #2

    alphysicist

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    Homework Helper

    Hi sid88,

    The gravitational potential energy for this problem is U=mgy. The rate of change of U is the rate of change of mgy. Since m and g are constants, can you find the rate of change of y?

    Once you find that, a quick multiplication will give you the rate of change of mgy.
     
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