Statical equivalence between two mechanical actions: a force on the arm of a spanner, and the combination of a force and a torque directly on the nut (expression of a <a href="https://en.wikipedia.org/wiki/Screw_theory#Wrench_2" class="extiw" title="en:Screw theory">wrench</a> at two different points, see <i>Screw theory</i>)
<a href="//commons.wikimedia.org/wiki/User:Cdang" title="User:Cdang">Cdang</a>
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