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Thread: Physics Question

  1. #1
    Registered User Ghost's Avatar
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    Physics Question

    Feel free to be as pedantic about this as you want.

    A friend wants to know

    "If a lorry fully loaded with chickens weighs 5 tonnes. How much does it weigh if all the chickens start flying around in the back?"

    The chickens are free and can fly as much as they want to. The lorry is hermetically sealed with sufficient oxygen so they don't die. Schrodinger is elsewhere at the time.

    His basic question is that in order to fly there must be a downwards force and presumably this eventually acts on the floor, so the lorry still weighs the same. Apparently it's puzzled him for years.

    Oh and feel free to change tonnes to Newtons.

  2. #2
    Registered User NickC's Avatar
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    Re: Physics Question

    If the air in the truck is sealed then the lorry will always remain the same, but if can circulate with the outside world then the lorry weight will reduce by the wieght of the chickens

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    Lovely Moderator ducasi's Avatar
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    Re: Physics Question

    The truck will remain 5 tonnes – chickens can't fly!
    Let your mind go and your body will follow. – Steve Martin, LA Story

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    Re: Physics Question

    Quote Originally Posted by ducasi View Post
    The truck will remain 5 tonnes – chickens can't fly!


    And even if they could, since the truck is loaded to capacity, they wouldn't have room! (Hey - you did say to be pedantic )

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    Papa Smurf
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    Re: Physics Question

    yes, there are quite a few "issues" with the original post - "hermetically sealed"

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    Re: Physics Question

    Quote Originally Posted by Ghost View Post
    Schrodinger is elsewhere at the time.

    .
    and I suppose, his cat is causing the chickens to fly

  7. #7
    The Oracle
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    Re: Physics Question

    It has been 'tested' with pigeons

    http://mythbustersresults.com/episode77

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    Re: Physics Question


  9. #9
    Papa Smurf
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    Re: Physics Question

    Quote Originally Posted by philsmove View Post
    Slightly different though when its birds that can actually fly, with room to do so in a truck they can actually breath in The first post is a logic puzzle not a serious science experiment. The new scientist question link you gave at least gives you the option of scientific testing. The answer is Yes, he would make it across. Simply because the bridge limit is 5000 kilograms and the total weight is 5050 kilograms , barely over it - limits are "safe limits" not realistic limits. i'm no engineer but even I recognise a safe limit is going to be far removed from a structural collapse limit

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    Re: Physics Question

    Quote Originally Posted by Dreadful Scathe View Post
    - limits are "safe limits" not realistic limits. i'm no engineer but even I recognise a safe limit is going to be far removed from a structural collapse limit
    Not if it was a height limit.

    Not that it is of course.

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    Re: Physics Question

    Quote Originally Posted by Dreadful Scathe View Post
    Simply because the bridge limit is 5000 kilograms and the total weight is 5050 kilograms , barely over it - limits are "safe limits" not realistic limits. i'm no engineer but even I recognise a safe limit is going to be far removed from a structural collapse limit
    Nah, I was an engineer and we used to just add 1 for safety.

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    Re: Physics Question

    Quote Originally Posted by Gav View Post
    Nah, I was an engineer and we used to just add 1 for safety.
    I stand corrected and will not drive over Army bridges with pigeons ever

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    Re: Physics Question

    Is a pigeon driving the truck or is the driver not being taken in to consideration?

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    Commercial Operator StokeBloke's Avatar
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    Cool Re: Physics Question

    Sorry... I got here late.... just to recap.... are the chickens frozen?

  15. #15
    Forum Bombshell - Our Queen! Lory's Avatar
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    Re: Physics Question

    Has anyone taking into consideration the fact that they lay eggs?

    Surely the weight of the truck will depend on how many of the chickens still have the eggs inside when they fly, or if they leave them on the ground
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    Re: Physics Question

    And what about the weight of pidegon poop?

    Plus if the pidegons are flying, they are burning energy and will weigh less?

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    Registered User sunnybunny's Avatar
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    Re: Physics Question

    Do pidegons weigh more than pigeons ?

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    Re: Physics Question

    Quote Originally Posted by Lee Bartholomew View Post
    And what about the weight of pidegon poop?

    Plus if the pidegons are flying, they are burning energy and will weigh less?
    You are getting closer to the right answer, be it chickens trying to fly or pigeons flying, truck hermetically sealed or not.

    Action creates heat, hot air expands. Even if the truck is hermetically sealed it will expand slightly with less dense air inside, so it will be lighter.

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    Re: Physics Question

    Quote Originally Posted by Gav View Post
    Nah, I was an engineer and we used to just add 1 for safety.
    So when someone says: "How many women are you seeing at the moment?", you say "Two."

    Sounds distinctly unsafe to me...

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    Re: Physics Question

    Quote Originally Posted by bigdjiver View Post
    You are getting closer to the right answer, be it chickens trying to fly or pigeons flying, truck hermetically sealed or not.

    Action creates heat, hot air expands. Even if the truck is hermetically sealed it will expand slightly with less dense air inside, so it will be lighter.
    It certainly won't be lighter. It might be incrementally larger, but it won't be lighter.

    Anyway, a lighter is a type of cargo boat.

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