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Homework Help: Weight times density

  1. Feb 3, 2010 #1
    what does weight times density equal?

    Simple thread I know, but I couldn't find a straightfoward answer online.
     
  2. jcsd
  3. Feb 3, 2010 #2

    berkeman

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    Doesn't ring a bell. Where have you seen it used?
     
  4. Feb 3, 2010 #3
    I haven't, but surely it must equal something?
     
  5. Feb 3, 2010 #4

    berkeman

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    Please don't call me Shirley. :tongue2:

    And no, it doesn't have to be anything special or real. Just look at the units...
     
  6. Feb 3, 2010 #5
    :biggrin:

    Ok, what is the difference between volume and mass?

    Apologides for not starting a new thread, I'm sure you agree it would just be a waste of space.
     
  7. Feb 3, 2010 #6

    berkeman

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    Mass/Volume = Density. But surely you know that already...

    Why these specific questions? Are you studying something that is bringing them up?
     
  8. Feb 3, 2010 #7
    I know what I'm told.

    What is the difference between mass and volume?

    My knowledge on physics isn't extensive. Please forgive me. If you believe I am wasting your time, I apologise, it is DEFINATELY not my intention to do so, and I strongly apologise if I have offended you in any way. I am simply trying to make sense.
     
  9. Feb 3, 2010 #8

    berkeman

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    No offense taken. I guess you can say that volume and mass are two properties of an object. The volume and mass of an object are related to each other via another property of the object, which is its density. I'm not sure that there's much more to it than that.

    Are you familiar with the website www.wikipedia.org?[/url] It has useful pages on many introductory subjects. It's less reliable for more advanced subjects, but the intro subjects are generally treated pretty well. The wewbsite [url]www.HowStuffWorks.com[/URL] is also good for many subjects.
     
    Last edited by a moderator: Apr 24, 2017
  10. Feb 3, 2010 #9
    Force x mass / Volume? Useless as far as I know and if force = mass x distace / time²

    we get mass² x distance / (Volume x time²)

    thats a fun one.
     
  11. Feb 3, 2010 #10
     
    Last edited by a moderator: Apr 24, 2017
  12. Feb 3, 2010 #11

    fluidistic

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    A volume is a delimited region in a 3 dimensional space. For example a box and the space in it.
    The mass is a property of a particle/object, etc. So what makes mass is the existance of particles/bodies. ( I believe so!)

    Still confused? I find both concept pretty easy to understand, even if I can't define them well. (Like time and energy).
     
  13. Feb 3, 2010 #12
    Does everything hold mass?
     
  14. Feb 4, 2010 #13
    no. not everything has mass. All matter does though. You have energy, which has no mass. But volume is just as fluid explained, its a measurement of space. how much space does something hold? a certain volume. It is possible that the relationship you are having trouble with will be a little clearer if i relate mass and volume. Things cannot hold mass without having a volume. Density is just a ratio of mass to volume. When we say something is dense, that means it has a high mass per volume. It is the same as the way we describe speed as miles per hour.
     
  15. Feb 4, 2010 #14
    So is mass a metaphysical concept?
     
  16. Feb 4, 2010 #15

    DaveC426913

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    No. Why would you think so?

    Any type of matter has mass. Not everything is matter.
     
  17. Feb 4, 2010 #16
    Sorry I am so slow with myself. Forigve me for back treading.

    What about dark energy?
     
  18. Feb 4, 2010 #17

    DaveC426913

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    Well, we don't know what it is yet, but if it's energy, it won't have mass.
     
  19. Feb 4, 2010 #18
    Wouldn't that mean e=mc2 is wrong then?
     
  20. Feb 4, 2010 #19

    DaveC426913

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    No.

    Einstein's equation says that mass and energy are equivalent, not that they are the same thing.

    If you took a mass M and converted it to energy, the amount of energy you would get is Mc^2.
     
  21. Feb 4, 2010 #20
    I think I understand, energy does not consist of mass and the speed of light...right?

    e2a:
    Also this suggests to me, that anti matter, dark matter, negative matter are the same things. Is this the thought of the science community at present? Or do people consider them to be completely different things?
     
    Last edited: Feb 4, 2010
  22. Feb 4, 2010 #21

    DaveC426913

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    Right.
     
  23. Feb 4, 2010 #22

    fluidistic

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    I never heard of negative matter, but I know that anti matter and dark matter aren't considered the same thing. Why do you think so? As suggested before in the thread, check out wikipedia...
     
  24. Feb 4, 2010 #23

    DaveC426913

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    Antimatter is just like normal matter, except for the charges. If there's antimater out there, it'll be as visible as ordinary matter. No so with dark matter. We detect dark matter by its gravitational effect, but we cannot see it; it does not interact with light.

    I don't know what negative matter is.
     
  25. Feb 4, 2010 #24
    No I understand, thank you all.
    Dark matter is what I consider(ed) to be negative matter as it would be equivalent to having none/negative mass
     
  26. Feb 4, 2010 #25

    DaveC426913

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    OK, now you understand that darkmatter indeed has mass. That's its defining property. What we don't understand is why we can't see it.
     
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