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Homework Help: Physics behind a fan based flying car concept

  1. Apr 12, 2012 #1
    1. The problem statement, all variables and given/known data

    For decades, people have dreamed of cars that can fly. You are part of a team which hopes
    to build the worldʼs first commercial flying car.
    Your proposed design has four fans, each of radius 50cm. Each fan sucks in air from above
    the car and blows it downwards. The downward flow of air can be approximated as a column
    of radius equal to that of the fan, traveling at a uniform speed downwards.

    How fast must the air be blown downwards if the car plus passengers weigh 1000 kg?
    You may assume that the density of air is 1.2 kg m-3.

    2. Relevant equations

    3. The attempt at a solution

    I have considered pressure differences, and conservation of angular momentum, but I cant seem to apply them in any way that helps me solve for the required unknown.
  2. jcsd
  3. Apr 12, 2012 #2


    User Avatar

    Perhaps if you thought of the car as a rocket.
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