# finding reactions(engineering)Watch

#1

Right, I know that you need to convert the masses into their weight equivalents (N) but I don't know where to go from there. Could someone explain how to calculate reactions for this structure?
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9 years ago
#2
take moments from about A including the weight of the beam to find reaction at B and then do the same about B to find reaction at A

if in equilibrium (as above) clockwise turning moments = anti-clockwise turning moments.

hope this helps
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9 years ago
#3
Well since the bar does not move, the forces pulling down on the bar are equal to the reaction forces.
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9 years ago
#4
yes but the reaction on A will be different to the reaction on B because of the positioning of the weight
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#5
I got the reaction of A=1972N and B=4601N. Can anyone check if this is correct?
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9 years ago
#6
(Original post by joeahuja)
yes but the reaction on A will be different to the reaction on B because of the positioning of the weight
Mark on the weight of the I-Bar, and then add 2 upward forces at the 2 reaction points

Take moments about one end to work out the reaction at the opposite end

Resolve the forces vertically to work out the other reaction force
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9 years ago
#7
yepits all bout moments as i said originally

and sorry but i got B=3717.99Nand A=2854.71N
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#8
hmm well how exactly did you work out the reactions?
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9 years ago
#9
I got and
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9 years ago
#10
(Original post by joeahuja)
yepits all bout moments as i said originally

and sorry but i got B=3717.99Nand A=2854.71N
These don't add up to 670gN
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#11
Mark on the weight of the I-Bar, and then add 2 upward forces at the 2 reaction points

Take moments about one end to work out the reaction at the opposite end

Resolve the forces vertically to work out the other reaction force
Could you exemplify this? I dont understand how you would do this. CHeers.
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9 years ago
#12
These don't add up to 670gN
errr yes they do 670 x 9.81 = 6572.7

and

3717.99 + 2854.71 = 6572.7
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9 years ago
#13
(Original post by joeahuja)
errr yes they do 670 x 9.81 = 6572.7

and

3717.99 + 2854.71 = 6572.7
lol i used 9.8 instead of 9.81

schoolboy error
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9 years ago
#14
haha i'm probs just being overly keen!! but my teacher is a 9.81 nazi and would slap me silly (proverbially) if i didn't use it :P.
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9 years ago
#15
(Original post by joeahuja)
haha i'm probs just being overly keen!! but my teacher is a 9.81 nazi and would slap me silly (proverbially) if i didn't use it :P.
lol i'm still in M2 mode (and will be until my exam finishes tomorrow )
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9 years ago
#16
good luck with the exam...is M2 hard, i did M1 but didnt take further!...i'm more of a physics man myself!
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9 years ago
#17
(Original post by joeahuja)
good luck with the exam...is M2 hard, i did M1 but didnt take further!...i'm more of a physics man myself!
Cheers

I'm not doing further either - i'm doing C1-4 and M1&2

M2 can be a bit tricky but its quite easy IMO
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9 years ago
#18
oh rite i wish i cud've dun that we did M1 and S1 (gaah wot a borin part of maths that was) well hope you do well m8.
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9 years ago
#19
(Original post by joeahuja)
oh rite i wish i cud've dun that we did M1 and S1 (gaah wot a borin part of maths that was) well hope you do well m8.
That must be quite annoying for you (being a physics and all lol)

I hope so too i guess id better go off and revise now instead of wasting time on here (again)
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