Notices
Results 1 to 10 of 10

Thread: How is this possible?!

  1. #1 How is this possible?! 
    New Member
    Join Date
    Aug 2010
    Posts
    2
    How is it possible that people/animals are able to have sufficient energy to move/consume energy all day by eating food and take enough rest?!

    I figured that if we know how this works we can apply this to so much things. Even a fly can fly around all day by eating tiny bits... I know that animals/humans are very efficient, but how do we have enough energy by eating food/taking enough rest? To move something with electronics you need so much more then the calories burned by a human.

    I couldn't google this, so I thought I'd ask this forum, see what results we can get!

    I'm new! Hello everyone =]


    Reply With Quote  
     

  2.  

    Related Discussions:

     

  3. #2 Re: How is this possible?! 
    Forum Ph.D. Leszek Luchowski's Avatar
    Join Date
    Jun 2008
    Location
    Gliwice, Poland
    Posts
    807
    Quote Originally Posted by OnlineHobo
    To move something with electronics you need so much more then the calories burned by a human.
    Did you try to do the math? How many AA batteries equal the energy (a.k.a. calories) in one decent meal?


    Leszek. Pronounced [LEH-sheck]. The wondering Slav.
    History teaches us that we don't learn from history.
    Reply With Quote  
     

  4. #3 Re: How is this possible?! 
    New Member
    Join Date
    Aug 2010
    Posts
    2
    No, did you?
    Reply With Quote  
     

  5. #4  
    Suspended
    Join Date
    Apr 2007
    Location
    Pennsylvania
    Posts
    8,795
    The efficiency of human muscle has been measured (in the context of rowing and cycling) at 18% to 26%.[15] The efficiency is defined as the ratio of mechanical work output to the total metabolic cost, as can be calculated from oxygen consumption.
    http://en.wikipedia.org/wiki/Muscle#Efficiency
    Reply With Quote  
     

  6. #5  
    Universal Mind John Galt's Avatar
    Join Date
    Jul 2005
    Posts
    14,168
    Dear online hobo,
    welcome to the forum. You have asked an interesting question. Leszek has given you a very helpful answer. It is helpful in several ways.
    1. He has pointed you towards the fact that energy contained in a meal is considerably more than that contained in a couple of batteries. (You really ought to try the calculation. You will find it very informative. If you are having difficulty then I am sure several people would be pleased to help.)
    2. He has introduced you to an important part of the scientific process: that's the part where you seek to quantify what you are studying.
    3. He has given you the opportunity to learn through doing, rather than through simply being told.

    You seem to have misunderstood this and have responded rather rudely. Perhaps now you see the help Leszek was offering you, you will thank him.
    Reply With Quote  
     

  7. #6  
    Forum Cosmic Wizard i_feel_tiredsleepy's Avatar
    Join Date
    Mar 2008
    Location
    Montreal
    Posts
    2,256
    It would take approximately 12 bananas to power a standard automobile engine for an hour, gasoline is much more cost-effective.
    "I almost went to bed
    without remembering
    the four white violets
    I put in the button-hole
    of your green sweater

    and how i kissed you then
    and you kissed me
    shy as though I'd
    never been your lover "
    - Leonard Cohen
    Reply With Quote  
     

  8. #7 Re: How is this possible?! 
    Forum Ph.D. Leszek Luchowski's Avatar
    Join Date
    Jun 2008
    Location
    Gliwice, Poland
    Posts
    807
    Quote Originally Posted by OnlineHobo
    No, did you?
    No I didn't. But I'm pretty sure a good meal will be worth a lot of batteries.

    Ophiolite, I'll give OnlineHobo the benefit of the doubt and assume he was not being rude - just asking if I had investigated the steak&noodles vs batteries equation and had a ready answer, which would save him some time.

    Online, if you do find out, please let us know. I'm curious, but just can't afford the time to look for it myself.
    Leszek. Pronounced [LEH-sheck]. The wondering Slav.
    History teaches us that we don't learn from history.
    Reply With Quote  
     

  9. #8 Re: How is this possible?! 
    Universal Mind John Galt's Avatar
    Join Date
    Jul 2005
    Posts
    14,168
    Quote Originally Posted by Leszek Luchowski
    Ophiolite, I'll give OnlineHobo the benefit of the doubt and assume he was not being rude - just asking if I had investigated the steak&noodles vs batteries equation and had a ready answer, which would save him some time.
    You are probably correct. Put my terse post down to jet lag and being awake at 3.00 in the morning local time.
    Reply With Quote  
     

  10. #9  
    Suspended
    Join Date
    Apr 2007
    Location
    Pennsylvania
    Posts
    8,795
    An alkaline AA battery has a voltage of about 1.5 volts and capacity of up to 3000 milliamp-hours. That works out to 4.5 watt-hours. A watt-hour is 3600 joules, and a kilocalorie is 4.184 kilojoules, giving about 3.87 kilocalories per AA battery. It would take 98 AA batteries to equal the energy of 1 medium order of McDonald's french fries.
    Reply With Quote  
     

  11. #10  
    Forum Ph.D. Leszek Luchowski's Avatar
    Join Date
    Jun 2008
    Location
    Gliwice, Poland
    Posts
    807
    I couldn't resist the temptation and did the maths, very crudely, and I do not guarantee I didn't make a mistake somewhere.

    My assumptions:

    - the recommended daily calorie intake is a little more than 2000 "big calories" (a very confusing term used by dietitians, which means kilokalories)

    - an alkaline AA battery has a charge of approx. 2700mAh at a voltage of 1.5V.

    My result was that we would need something at the order of 600 batteries a day to replace the energy we get from food. That's about 1 battery every 2 minutes.

    Again: this is a very careless estimation which may be totally wrong. Don't blame me if have 150 batteries for breakfast and starve to death after just 10 minutes.

    PS: I notice Harold has been at it as well; his results look similar - a sixth of the number of batteries for a serving of fries that may plausibly carry a sixth of the recommended daily calorie intake.

    None of the above is meant to encourage anyone to rely on fast food for their nutrition.
    Leszek. Pronounced [LEH-sheck]. The wondering Slav.
    History teaches us that we don't learn from history.
    Reply With Quote  
     

Bookmarks
Bookmarks
Posting Permissions
  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •