Working out reaction forces in moments

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mxx454
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So i’m working through a few moments exam questions and i’ve noticed when e.g working out reaction forces and working with weight sometimes the weight is X 9.8 but others it’s left in newtons and i’m confused when to add the g and when to leave in newton’s. Like for 9a) i did 200g but the mark scheme only used 200 so they ended up getting 125N and i ended up getting 1225.Name:  D06D5FF9-60DF-486E-9A5B-605E8259F66E.jpeg
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0le
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I am not actually sure how to answer the questions, but g has the units of an acceleration and N has the units of a force. You are most likely getting muddled up somewhere on this point.

EDIT:

Okay, so the first one, take the moments about point A and assume the weight (a force) of the beam acts downwards at its center.

Then assuming the beam is in equilibrium and not rotating, take moments about point A with clockwise being positive. You have:


(2.5).200 - (4)C = 0.

The numbers in brackets are the distances in meters and both 200 and C are forces with the unit N. C must therefore be a force in units and you get 125N.
Last edited by 0le; 4 weeks ago
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