Another Airplane Physics Question | FerrariChat
Buy

Another Airplane Physics Question

Discussion in 'Other Off Topic Forum' started by Dubya, Jan 19, 2014.

This site may earn a commission from merchant affiliate links, including eBay, Amazon, Skimlinks, and others.

  1. Dubya

    Dubya Karting

    Jun 30, 2013
    114
    Sydney, Australia
    #1 Dubya, Jan 19, 2014
    Just read the other Airplane question, and thought of another!

    If a plane was flying along and it was carrying 5000kg of birds.

    If all the birds flapped their wings at the same time and became airborne inside the cabin, would the plane now weigh 5000kg lighter?
     
  2. wax

    wax Five Time F1 World Champ
    Lifetime Rossa

    Jul 20, 2003
    52,412
    SFPD
    Full Name:
    Dirty Harry
    #2 wax, Jan 19, 2014
    Their vortexes would quickly cancel each other out, let alone ensuing birdie Air Traffic Chaos might make pilot wish it were filled with rabid, starving bats & terrified skeeters & gnats.

    ------

    If an empty Airbus cruising at altitude is filled with water & flying fish from an aircraft tanker . . .


    Sent from my iPhone using Tapatalk
     
  3. Dubya

    Dubya Karting

    Jun 30, 2013
    114
    Sydney, Australia
    #3 Dubya, Jan 19, 2014
    Okay... I have another......

    We all know that as an aircraft burns fuel, it gets lighter, and as a consequence it will burn even less fuel per nautical mile covered (it's called Specific Ground Range).

    If we used hydrogen as a fuel, you would think that the aircraft would be at its lightest state at takeoff, and then get heavier as it burns it's fuel.

    True concept, or false?
     
  4. toggie

    toggie F1 World Champ
    Owner Silver Subscribed

    Nov 30, 2003
    19,036
    Virginia
    Full Name:
    Toggie (Ron)
    #4 toggie, Jan 19, 2014
    Yes, and that physics question was proven with the Hindenburg accident.

    The hydrogen inside the Zeppelin burned and it stopped floating in the air and sunk to the ground (that is, it got heavier).
    .
     
  5. Dubya

    Dubya Karting

    Jun 30, 2013
    114
    Sydney, Australia
    #5 Dubya, Jan 27, 2014
    Toggie...... I like your reasoning.
     
  6. texasmr2

    texasmr2 Two Time F1 World Champ
    BANNED

    Oct 22, 2007
    22,232
    Houston
    Full Name:
    Gregg
    #6 texasmr2, Jan 27, 2014
    YES!!!

    I win again!!

    Just checking!!
     
  7. Pass

    Pass F1 World Champ
    Silver Subscribed

    Feb 29, 2008
    13,143
    Salida Colorado
    Full Name:
    Mark Passarelli
    #7 Pass, Feb 8, 2014
    False if the air space holding the hydrogen draws a vacuum. The hydrogen is considered neutral buoyancy then.
     
  8. Airspeed

    Airspeed Karting

    Sep 13, 2005
    60
    DSM IA / Minneapolis
    Full Name:
    Kenton
    #8 Airspeed, Mar 3, 2014
    Last edited: Mar 3, 2014
    Air is a fluid. In a pressurized cabin it's like a coke bottle filled with water with the lid on it and a tiny fish inside. If you consider that the birds are suspended by the air inside of the effectively sealed-in air inside of the cabin in the same maner that a fish is suspended in the fluid you can not come to the conclusion that it plane would get lighter.

    (Assuming that the cabin was at a relatively high differential pressure as compared to the air outside. Normal cabin differential is about 8.4 psi in cruise flight so the plane would loose a little more than half of the 5,000 lbs since sea level pressure is approximately 14.7 lbs. The pressure at 18,000 feet is roughly half that, and becomes even less with altitude.)

    In an unpressurized plane...It probably would get lighter due to equal air pressure inside and outside of the plane. In that case the wings would be acting solely upon ambient air pressure in the same way that an open bottle underwater wouldn't know if a fish was inside of it or not. The fishes displacement would equal that of water.



    Best Answer. ;)

    You're welcome
     

Share This Page