#1
First off, this is not really a "do my homework for me" thread. More of a "do my homework for my douchebag friend" thing. I know explaining it is futile because regardless of what I say, I know nobody will be conviced that it's not actually for me. To explain it simply, my friend has something thing I want, and I'll get it if I do this for him. I'd do it myself but I have a ton of homework to catch up on myself and haven't ever done any physics myself, thus making me completely lost with most of these questions. Anyway, help is sincerely appreciated, and if not then it's completely understandable.

1. Define tension and compression and explain how materials react to these types of forces
2. Define the three types of stresses a material experiences when forces are applied to the material
3. How do scientists test materials to obtain a stress-strain curve
4. Why should Newton's Third Law of Motion be a concern to engineers when designing a bridge and explain an action and reaction pair of forces
5. Explain the concepts of equilbrium, static and dynamic loads, vibrations, and resonance in regards to the types of bridges
6. Identify the following types of bridges (main features): truss, arch, and suspension

I know this is stupid, but any assistance is truly appreciated.
#2
lol those aren't easy questions. You are looking for Mechanical and Civil Engineers. Mechies and Civies of the Pit, arise.
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#3
I think they may be convinced it's not you, but now you're making people work for your douchebag friend?

That was smooth.
#5
Maybe douchebag was an inappropriate word

I need something from him, he needs a favour from someone. Fair trade, I'd say. Except for the kind individual willing to assist me, who's only reward will be my eternal gratitude towards said person.
#6
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First off, this is not really a "do my homework for me" thread. More of a "do my homework for my douchebag friend" thing. I know explaining it is futile because regardless of what I say, I know nobody will be conviced that it's not actually for me. To explain it simply, my friend has something thing I want, and I'll get it if I do this for him. I'd do it myself but I have a ton of homework to catch up on myself and haven't ever done any physics myself, thus making me completely lost with most of these questions. Anyway, help is sincerely appreciated, and if not then it's completely understandable.

1. Define tension and compression and explain how materials react to these types of forces
2. Define the three types of stresses a material experiences when forces are applied to the material
3. How do scientists test materials to obtain a stress-strain curve
4. Why should Newton's Third Law of Motion be a concern to engineers when designing a bridge and explain an action and reaction pair of forces
5. Explain the concepts of equilbrium, static and dynamic loads, vibrations, and resonance in regards to the types of bridges
6. Identify the following types of bridges (main features): truss, arch, and suspension

I know this is stupid, but any assistance is truly appreciated.



I'm a mechanical engineering student. Just going from memory here.

1. Tension - stretching something (axial force outwards), compression is opposite. Depending on their properties (brittle, tensile, etc.) they will react in different ways to them.
2. There's shear, normal, and... and... its escaping me
3. Did it last term, forgot how. Sorry.
4. Ask a civie, but its all to do with force couples. Otherwise the bridge supports would sink straight thru the earth, and that just isn't logical.
5&6. Christ, we have whole courses on this stuff, you know that right? Really, its VERY complicated (well not equilibrium and static, but dynamics and vibes is hell on earth). Google it, or get a decent textbook.

Also, ask a civie.
#7
Heres 3. I just got my Master's in Mechanical Engineering and am currently in a Ph.D. program. You can obtain a stress-strain curve doing a simple tension test (uniaxially load the member). From this you can determine the elastic range (where stress is directly proportional to strain) and other material properties such as poisson's ratio, modulus of elasiticity and shear modulus. Also you can obtain the yield stress and ultimate stress and with some practice can determine is a material is ductile, brittle, visco-elastic, etc.
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#10
We did a brief overview of the physics behind bridges in my high school engineering class recently, so I can help with a few of the questions but not all of them:

1. Define tension and compression and explain how materials react to these types of forces:
Tension = the magnitude of the "pulling" force exerted on an object.
Compression = the magnitude of the "pushing" (compressive stress) force exerted on an object.
Materials undergoing tension will often stretch out until it reaches its breaking point. Those undergoing compression will generally collapse under the force.

2. Define the three types of stresses a material experiences when forces are applied to the material
1. Tensile stress - Stress when two forces act on an object but point away from each other (think pulling)
2. Compressive stress - Stress when two forces act on an object and point towards each other (pushing)
3. Shear stress - Occurs when two objects slide against each other

4. Why should Newton's Third Law of Motion be a concern to engineers when designing a bridge and explain an action and reaction pair of forces
An action/reaction pair are two forces of the same magnitude that act in the opposite direction of one another. Given a sample bridge, on each 'point' (anywhere a bolt would be located), there are various tension/compression forces acting on that point. To find the net force on the point, you have to take into consideration all the forces acting on that point from each of the bars that act on that point. Having knowledge of Newton's Third Law is essential to this process because if a given bar exerts a force of magnitude F on a certain point, the bar will exert a force of the same magnitude on the other point it is connected to, just facing the opposite direction. This knowledge of forces is crucial to finding the net force on each point of the bridge in order to ensure no point is receiving too much stress.

We didn't discuss 3, 5, or 6. For 3, we went over a stress-strain curve but not how materials were tested for it, just how to interpret it.
Hope I helped a little...not that it matters since by the time this is posted there will probably have been 5 other people posting the same thing.
Last edited by johnthebassist4 at Jan 12, 2012,
#11
This is great, honestly. Incredibly helpful. I have 1-4 done and am currently working on a very poorly done 6 I did not expect such high quality answers. It seems that 5 is an insane demand to make, according to some. I know I'm pushing my luck here, but this thread has already exceeded my expectations, I hope it's not much to ask. 5 can be as abbreviated and horribly done as you wish, it's just more important to have it done. Also, 6 would be nice. Only the very basic features need to be mentioned. Basically, what major things seperate the three from each other.

It may be a bit of a demand, but it's greatly appreciated. Honestly
#12
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lol those aren't easy questions. You are looking for Mechanical and Civil Engineers. Mechies and Civies of the Pit, arise.
Well it's a-level standards-ish but it's late and johnthebassist4/hawk5211 probably covered everything (too tired to check). The important thing is that I don't think that you are doing this through the right morals... blah blah... etc...
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#13
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#14
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and... and...

Bending moment.
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