ext_8821 ([identity profile] lederhosen.livejournal.com) wrote in [personal profile] lederhosen 2005-04-04 12:32 pm (UTC)

That's one of the things that pisses me off - even if you figure out that the 's' might stand for 'squared unit of length' (which is what it *has* to be, if the 'g' is a gram-force), the abbreviation still leaves no way to tell *what* unit of length. The centimeter-gram-second system is the bane of my existence, I hate it worse than imperial units.

Stress and strain are closely related quantities. Strain is unitless - it refers to the stress-induced deformation of an object proportional to the size of an object. (If you take a 1m cube and squish it so it bulges out to 1.01m, the strain is 0.01.)

Stress is the associated internal force per unit area, measured in pascals (same as pressure). If I take a wire of cross-sectional area 1E-6 m2, and use that to support a mass of 1 kg (i.e. a force of about 10 newtons), the associated strain is 10/1E-6 = 1E7 pascals. (Assuming it's distributed evenly through the cross-section of the wire, which it probably isn't.)

Note that both stress and strain are direction-dependent quantities.

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