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How to create heat using a falling object?

  1. May 30, 2014 #1
    Hello!

    I am trying to think of ways to generate significant amounts of heat through the motion of a falling object? Let's say we have a heavy ball and a structure that enables it to fall from a height of 30m for instance, how would you go about creating heat? I suppose you would have to use friction and materials that heat up easily?

    Thanks!
     
  2. jcsd
  3. May 30, 2014 #2
  4. May 30, 2014 #3
    Thanks paisiello2!

    So I imagine the friction of the weight on the right heats that poll? Do you know the type of material used? And to what degree it can heat if repeated?
     
  5. May 30, 2014 #4
    I think you are limited by gravitational potential energy. You need a lot of mass or a very far falling distance to get significant heat. I'm thinking like a meteor. The medium is useful for extracting the heat (which is what I think the apparatus above is doing) but its not going to generate any more heat. Too viscous of a medium and your object will come to a stop.
     
  6. May 30, 2014 #5
    No, the motion of the pallets in the water will heat up the water. There is no pole on the right hand side. Just a ruler to measure the height.
     
  7. May 30, 2014 #6
    Thank you so much nasu, I was way off! haha That's interesting, but I assume it wouldn't heat the water much, even if it were repeated many times, right?

    Thanks ModusPwnd, I see what you're saying. So all in all, it's not possible to create much heat simply using falling objects (unless we're talking of huge scales, like a meteors).
     
  8. May 30, 2014 #7

    russ_watters

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    ...or hydroelectric dams.
     
  9. May 31, 2014 #8

    NascentOxygen

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    You could just keep dropping something onto a block of lead, that will transfer most of the kinetic energy into heatng of the metal.
     
  10. May 31, 2014 #9
    It's measurable.
     
  11. May 31, 2014 #10

    russ_watters

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    I worked on a cooling plant at a chocolate factory: big vats (vw bug sized) where they ground beans and stirred mixtures had 100 kW motors and needed water cooled jackets to keep from burning the chocolate.
     
  12. May 31, 2014 #11

    sophiecentaur

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    They used to have a quantity called the "Mechanical Equivalent of Heat" when I was a lad. (We have the same thing now but it isn't given that descriptive name).
    It is 4.2 Joules per Calorie.
    Now, a Joule is the energy needed to lift 0.1kg (weighs one Newton) by 1m. Quite an appreciable and could-be-useful bit of work.
    A Calorie (Not the 'calorie' on food packaging - which is one kilocalorie) is the energy needed to raise the temperature of just 1g of water by 1 degree C - a hardly noticeable quantity of heat.

    You need a lot of useful mechanical work to provide a not really useful amount of heat.
    Russ's 100kW motors (100kJ per second!!) were really serious pieces of kit (motorcar engine sizes). There are not many places where you can get that sort of Power from 'a falling object'. Hydroelectric power stations are the only things that come to mind as constant sources of serious amounts of Power from falling objects.
     
  13. Jun 1, 2014 #12

    NascentOxygen

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    More durable would be a cylinder of air with a piston uppermost but sealed at the base. The falling weight would compress the air, heating it. A water jacket would extract the heat. (Remember pumping up your bike tyres?)
     
  14. Jun 1, 2014 #13

    CWatters

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    Easy to work out...

    1kg falling 30m can provide about 1*9.8*30 = 300 Joules approx.

    Enough to heat 1kg of water by about 300/4181 = 0.07 degrees.
     
  15. Jun 1, 2014 #14

    sophiecentaur

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    The problem is to find a significant source of 'dropping objects'.

    I remember hearing about the original slaughterhouses in Chicago (millions of animals to feed the US population). The whole system was worked by the energy of the animals walking to the top of a multi-storey building. They were carried down the production line by gravity on a sloping rail with chops and steaks appearing at the bottom. Bummer of an energy source, as far as the cattle were concerned, eh?
     
  16. Jun 1, 2014 #15
    Use a fire piston and a falling weight to depress the piston.
     
    Last edited by a moderator: Sep 25, 2014
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