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A particle is a minute fragment or quantity of matter. In the physical sciences, the word is used to describe a small localized object to which can be ascribed several physical or chemical properties such as volume or mass; subatomic particles such as protons or neutrons; and other elementary particles.〔 〕 The word is rather general in meaning, and is refined as needed by various scientific fields. Something that is composed of particles may be referred to as being particulate.〔 〕 However, the term particulate is most frequently used to refer to pollutants in the Earth's atmosphere, which are a suspension of unconnected particles, rather than a connected particle aggregation. ==Conceptual properties== The concept of particles is particularly useful when modelling nature, as the full treatment of many phenomena is complex.〔 〕 It can be used to make simplifying assumptions concerning the processes involved. Francis Sears and Mark Zemansky, in ''University Physics'', give the example of calculating the landing location and speed of a baseball thrown in the air. They gradually strip the baseball of most of its properties, by first idealizing it as a rigid smooth sphere, then by neglecting rotation, buoyancy and friction, ultimately reducing the problem to the ballistics of a classical point particle.〔 〕 The treatment of large numbers of particles is the realm of statistical physics.〔 〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Particle」の詳細全文を読む スポンサード リンク
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