For a Torque/ Equilibrium question : Pivot/ Moment POINT

Hello. For this style of question can you also clarify HOW do you SPECIFICALLY determine the Moment / Pivot point in a beam. Will the exam paper always tell you. Thank you

Hi @sphysics ,

No, the question will often tell you what to use as a pivot, but you could be expected to identify it yourself. I would think about it as the point that a lever (bridge, seesaw, beam) would rotate around. This is easier when there is only one support. Where there are two supports (eg. bridges) you could treat either support as a pivot and work out your answer from there. Essentially, the bridge could rotate about either support - if the other support was removed. In this situation, if you are asked to calulate the support force of ‘A’, then you would use ‘B’ as your pivot.

It may be easier to understand with a short video. Have a look at these examples and let me know if you have any more questions.

Best wishes for your revision.