You do it so quickly that the heat flow between the inside of the bicycle pump and the outside is too slow compared to the speed at which you compress.

我们用力很大,于是压缩得很快,打气筒内外热传递的速度,与之相比要慢得多。

麻省理工公开课 - 热力学与动力学课程节选

Therefore, it'll compress by an unknown x, which is equal to mg divided by the force constant of the spring.

因此它的压缩量为 x,也就等于 mg 除以弹簧的弹性系数

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