# Mechanical Principles -- Assignment question

• Al_Pa_Cone
In summary, the conversation revolves around a question regarding a simply supported beam with a specific length and Young's Modulus. The first two parts of the question involve drawing a shear force diagram and determining the position and magnitude of the maximum bending moment. The conversation then shifts to the third part of the question, which asks for a graph of deflection along the length of the beam calculated at 1 meter intervals. The conversation includes discussions of equations and methods for solving the question, as well as clarifications and suggestions for improvement.
So I think I have the correct method now by inputting my values for x into the formula for each point on the graph with the knowledge that A already sums to -76 for each value of x and B would be the graph plotting figure remaining in from the formula.

I am determined to get this question right as I have spent so much time on it! Really thanks for everything. I would have never been able to get through this on my own. As I am a distance learning student, I don't have any others around me to bounce questions off nor a tutor to quiz when I get stuck. If I don't fully understand the text then I have to just figure it out elsewhere. So thanks so much for all your time!

Al_Pa_Cone said:
B would be the graph plotting figure remaining in from the formula
Not sure what you mean by that. Just substitute B=0 and A=-76 in your general equation for EI y as a function of x. Then evaluate for whatever values of x you want.

Al_Pa_Cone
Hey, for part b), an easier approach is to sketch the bending moment diagram, which will be continuous since there are no applied external moments, and then, the maximum bending moment will be located along the beam where the shear diagram is 0. So, you don't need to write all those algebraic equations. Why? Because the moment diagram is the integral of the shear force function over the span of the beam.

Al_Pa_Cone and haruspex

Well this is what I have managed to obtain for the method I think I am following correctly. For plotting values at 1 meter increments I now have all positive values for B??
it does however make the arch on a graph, showing it would fit within the deflection diagram #29 if the values had all been Negative?

Maybe I am being stupid, Does B always = 0 throughout the equations, an the values would read
EI y = -74.6 + 0 for x = 1 therefore the plotting point would be -74.6 and no further transposition would be required?

Al_Pa_Cone said:
, Does B always = 0 throughout the equations, an the values would read
EI y = -74.6 + 0 for x = 1 therefore the plotting point would be -74.6 and no further transposition would be required?
Yes.

Al_Pa_Cone
Well well well. Looks like the answer does exist! Thank you so much for your patience. You are a very helpful Tutor and I certainly would not have managed that without your guidance. All the best for the New Year as well!

Al_Pa_Cone said:
Well well well. Looks like the answer does exist! Thank you so much for your patience. You are a very helpful Tutor and I certainly would not have managed that without your guidance. All the best for the New Year as well!
You are welcome. I learned something too.

Sorry to drag this back up.

I am following the question here but getting vastly different results.
Bending at the 1m mark of 625mm which obviously looks wrong.

Going right back to post #1, I have calculated I as being;

## I = \frac {0.03*0.06^3} {12} ##
## = 0.54*10^{-6} ##Jumping back to the later posts I have the same formula for IEy= ... as post #39I see the poster omitted (red writing) parts of the formula that was to the right of the part in question but kept the rest of formula in. Why is that?
Using that method though, I then calculated ##y ##by dividing the result by EI. (210x##10^9## x 0.54x##10^{-6}##
Leaving these horrifically high numbers.
1m = -0.657m

Any help appreciated.

Last edited:
hey guys i was doing this question but don't understand anything and how it works can i get some help i tried to follow the working out in my notes and one of the al_pa_cone.
still don't understand some help will be great.
thank you

thor55 said:
hey guys i was doing this question but don't understand anything and how it works can i get some help i tried to follow the working out in my notes and one of the al_pa_cone.
still don't understand some help will be great.
thank you
Which post by al_pa_cone, and where is the first part you do not understand?

basically i know that this is a simultaneous equation but like when the integration takes part and the denominators change in post 20
and when he( al_pa_cone) works everything out he has 12 as a dominator in post 24
also when he works out the value for A he has different denominators and that is what is confusing me as to how come there are different denominators
and also the in one of the post i believe you mentioned that if there is a negative number then the term should be ignored bit more info on that too.
because i used used skyciv free calculator and the deflection was towards the bottom and should not be positive
help will be appreciated.
Thank you

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