Mechanics of Materials basic exercise

In summary: F. So the total force is 5.0F.In summary, the students are trying to calculate the tensile stress on a beam, but need to find the cross section of a cylinder first. The students correctly found the cross section of a cylinder and calculated the tensile stress using the appropriate equation.
  • #36
We had a lab session where we tested hook's law until the breaking point of a brass specimen, so no exercising. We'll probably solve it tomorrow. The teacher actually said I'm jumping ahead of myself since we haven't learned the basics of solvng that (which makes me feel less stupid :smile: ) but regardless he told me my answer is wrong. Too bad I forgot too scan it last night. But, it appears to be wrong at any rate.

I don't understand.
In the picture you have 2 free bodies.
And each free body has all forces = 0 (since this is statics).

OK let's see if I got the basics mechanics right now.

http://img526.imageshack.us/img526/8374/nafix.jpg
 
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  • #37
Femme_physics said:
We had a lab session where we tested hook's law until the breaking point of a brass specimen, so no exercising. We'll probably solve it tomorrow. The teacher actually said I'm jumping ahead of myself since we haven't learned the basics of solvng that (which makes me feel less stupid :smile: ) but regardless he told me my answer is wrong. Too bad I forgot too scan it last night. But, it appears to be wrong at any rate.

Cool! So you got to break stuff? :cool:
Femme_physics said:
OK let's see if I got the basics mechanics right now.

http://img526.imageshack.us/img526/8374/nafix.jpg

You got the complete picture right with the proper normal force from the wall. :)

Your picture (b) is right too.

But in your picture (a) you have attached N to the wrong side of cylinder 2.
The cylinder is fixed on the left side, so it's only there that N can push.
 
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  • #38
Actually, when tensional forces are calculated, usually a diagram like the following is made.

That is, first all external forces are charted and calculated.

Then a cylinder is sawn into half, and the force H is figured out to keep the system in balance.
This is the force used to calculate the tensional stress.

Then the other cylinder is sawn into half, and the process is repeated.

attachment.php?attachmentid=40829&stc=1&d=1320914233.gif
 

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  • #39
Cool! So you got to break stuff?

Yes, made a big "BANG" sound and scared the shizzle out of me!

Anyway, thanks!

I'll print your last reply now and look at it in class (starts in 1 hr). Can see what I did wrong, We'll probably solve it today. Will reply later. Thanks :smile:
 
  • #40
Did you solve it today?
 
  • #42
Nice!
Complete with a graph for the expansion and a neat table!

Did you do all that by yourself?
 
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  • #43
I like Serena said:
Nice!
Complete with a graph for the expansion and a neat table!

Did you all that by yourself?
:smile:

No actually the teacher did. But hey, at least I know how to do them now and am ready for new challenges!

Thanks a lot, Klaas! I love the fact it's based on mechanics...bringing back those good ol' days... *grins*
 
  • #44
Femme_physics said:
:smile:

No actually the teacher did. But hey, at least I know how to do them now and am ready for new challenges!

Thanks a lot, Klaas! I love the fact it's based on mechanics...bringing back those good ol' days... *grins*

Oh, you'll get your challenges...
Wait till you get to load, shear, and moment diagrams!

(Poor little cartoon men! :eek:)
 
  • #45
LOL. Yea, for now, I keep practicing basic exercises. I'll scan my latest one this afternoon if you'll be here.
 
  • #46
I'll take a look at it when you get to it...
 

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