AEM 2021 Lecture Notes - Lecture 25: Length Overall, International System Of Units, Cross Product
17 May 2017
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Recall- for particle, condition of equilibrium is r=sum of forces=0. Expresses that systems of forces have zero net tendency to translate particles. For equilibrium- must prevent both translation and rotation. So, must study tendency of system of forces to cause rotation, leads to moment of a force. Goal- find tendency of f to cause body to rotate about o. Experience teaches tendency to cause rotation proportional to both. So,tendency to cause rotation of f about d. define moment of f about o. Refine by distinguishing cw from ccw rotation to find direction, use inspection of the diagram. Peasant units are foot pounds lb ft (or lb in) From definition of moment, clear that sliding f along loa won"t change moment won"t change tendency to rotate. Since the distance has been slid along loa, the rotation will be the same. F,d same same mo, same tendency to rotate. Same tendency to translate, same moment same tendency to rotate).
