Chapter 49.5

[uzairsyedahmed]

for question no 5.

There is normal stress which is due to Mz and another due to My. in the fourth quadrant they both act in same direction. Why shouldnt we just add them up plainly to get max tensile stress and take a resultant? Can anyone explain?

Thanks!

 

[nsgoldberg]

Adding them together would act as if the vector for the two were exactly the same. But one acts in the y-direction, and one in the z-direction. They both create a tensile stress in the 4th quadrant, but you cannot directly add them. That's why you must find the magnitude of the two. Draw a vector triangle and it should become more apparent.

 

[SNAPE/SMOTT PE]

Thanks for answering nsgoldberg, I wanted to answer but I have a hard time putting explanations in words. I can 'see' the "tensile stress in fourth quadrant" from the figure, but couldn't put the words to it. Ugh, maybe I've been at it too long studying! And maybe that's why I've been getting strange looks when talking to people at work...my brain is fried! I really hope I pass in October, as I don't think I'll make another six months studying!

 

[uzairsyedahmed]

oh.. I got ya.. the tensile direction maybe the same for the 4th but the magnitudes are different for both of them for a given segment. Good luck Smott!. I really want to pass too as I would be really pissed with myself for starting so late ( started late July) when I had all the intention of doing so from May. I wish I found this forum before because I spent a couple of weeks studying the Math section :S

 

[SNAPE/SMOTT PE]

I hear ya! I had signed up to take the exam last April, and ended up backing out since I didn't feel I had time to prepare. Since then my dad has gone downhill with his health and I'm dealing with that on top of everything. I know I'm not going to get to cover everything I need too, I just hope I cover enough.

 

[uzairsyedahmed]

yeah.. I am trying to make sure I have gone through as much as I can with special attention to TFS sections/ sections with higher weightage. I am just hoping I am left with enough time in the exam to be able to figure out the ones I am not comfortable with.

 

[uzairsyedahmed]

I hope your dad recovers his health and wish him good health!

 

[uzairsyedahmed]

Also, on that accord, I think they got the subscripts for moments wrong in the problem. the 600 x 8 should be Mz , right? if you apply the right hand rule

 

[nsgoldberg]

Glad I could help.

I've found a lot of problems in the MERM practice book. But oh well, with a book that thick, it's bound to have issues!

I'm sure both of you will have no problem passing. I know you've been studying plenty, and I think the exam will be a breeze for you (as it should be myself).

 

[uzairsyedahmed]

I sure hope so! your giving it in october too? what afternoon section?

 

[nsgoldberg]

Yep, ME-MD emphasis. I'll be taking it in Pomona, CA.

 

[SNAPE/SMOTT PE]

I've had a road block on studying. My dad had a stroke and I've been busy dealing with things related to that...traveling out of state every weekend, signing power of attorney papers, and just everything in general that comes with dealing with this kind of situation. At this point I hope I've studied enough to pass, but wouldn't be surprised if I didn't.

 

[uzairsyedahmed]

oh.. I am sorry to hear that. How is he doing now? our prayers are with him. We still have 20 something days and I plan to shove it all in the last three as what i did recently seems to stick better than what i did a month ago. you could brush up your studies in the last week to have all your strengths on your tips.

 

[SNAPE/SMOTT PE]

Thank you! He's not what he used to be. When I get a little time, I'm reviewing what I can. I think everyone who takes the PE exam deals with the struggle of retaining so much information at once. Even with the choice of a depth in the afternoon there is a large base of information that could potentially show up on the exam.

 

[uzairsyedahmed]

yeah.. thats true. plus its a different thing to recall something on your tips in an exam and recalling it at your leisure. As long as we have gained the concepts and keep our focus in the exam, we should pass. Or atleast thats what my colleague who took it in April said