a particular mass

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forgoodorill

Senior Member
Chinese
Hi, everyone!
I read a book:

Consider a game of snooker. The cue ball has a particular mass, and is at rest. You hit the cue ball with the cue, with a particular force and in a particular direction(towards the black, say).

So what's the meaning of 'mass' here? I couldn't find a proper one in the dictionary. I guess it means 'condition' here. But the dictionary doesn't exist this one. Only similar one to this is: a large amount of something that has no particular shape or arrangement:

Thanks in advance! :)
 
  • entangledbank

    Senior Member
    English - South-East England
    Mass is the scientific term for what, outside of science, we call weight: a snooker ball has a mass of 100 grams, or whatever. In your sentence 'mass' is used because force and velocity and position are probably going to be discussed.
     

    heypresto

    Senior Member
    English - England
    It's the scientific meaning of mass.

    From the WR Dictionary: Physics [uncountable] the quantity or amount of physical matter of a thing as figured from its weight or from Newton's second law of motion. Abbr.: m

    Or the 'm' in E = mc2
     

    Keith Bradford

    Senior Member
    English (Midlands UK)
    There is no standard mass for snooker balls, but they all tend to be about 167 grammes. That is their mass everywhere in the universe.

    On earth, under earth gravity, they also weigh 167 grammes because this is where snooker (and the gramme) were invented. On the moon they weigh 28 grammes. In outer space they weigh nothing.
     

    kentix

    Senior Member
    English - U.S.
    To be very precise, grams are a measure of mass, not weight. If a snooker ball has a mass of 167 grams on Earth then it has the same mass on the moon and in space. Mass is an inherent property of an object.

    Weight comes from gravity acting on a mass. The standard metric unit of weight is the newton. A snooker ball on the moon has the same mass but weighs less because the gravity acting on it is less.

    Because in the past all weights were essentially measured at the earth's surface the concept of weight and mass was intermingled. So when people say something weighs 100 kilos they really mean it has a mass of 100 kilos, and therefore a weight of 980 newtons at the Earth's surface. As long as you don't leave the Earth's surface there's no difference and one can be used in place of the other. When you go somewhere else in the universe that changes.

    On the moon that same object would still have a mass of 100 kg but it's weight would only be 163 newtons (instead of 980).

    It's very important to distinguish between the two in physics problems.
     
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