What was the flaw in the design of the Tacoma narrows bridge that cause it to collapse?
im studying for a science exam and this was a question that we needed to find the answer to on our own. I've looked all over the internet, but its not on wikipedia or answers or any of the first couple of pages of google. i just need to know what was wrong with the bridge that allowed the wind to break it.
Could someone please help with tension/compression in bridges?
So, I get that a popsicle stick can take a large amount of tension, but much less compression, so you want to maximize the tension forces in the bridge. If a popsicle stick is under tension, does that mean that you don't have to worry about it at all really? So, I should spend extra popsicle sticks to make the parts being compressed stronger? Also, I'm kind of confused about the numbers on this bridge building website/program: http://www.jhu.edu/virtlab/bridge/bridge.htm Apparently the numbers are percents of something, percent of the load acting on that member? If that's the case, wouldn't they add up to 100%? Should I be trying to get the blue numbers (compression) as low as possible? Lastly, I made this on that website: http://i.imgur.com/SpPQa.jpg Any suggestions to lower compression?
How do you calculate the max load a balsa bridge can carry?
You don't say what grade level you are at, is this a middle school, high school or university level project? Would this be a truss bridge? There are online simulators that will give you some idea of the stresses in the members of a truss, here is one example: http://www.jhu.edu/virtlab/bridge/truss.... But since these programs generally use some idealizations (ideal pined joints and pure tension or compression loading) they will only give you a rough idea of what is happening in a real structure. By coincidence I bought a couple of books just a few days ago at a thrift store that cover the sort of things you need to know. That doesn't do you much good since you don't have them, but I bring the up as an example of the magnitude of the problem. One book that is at hand is; Elementary theory of structures 3rd ed. by Yuan-Yu Hsieh, a 400 page textbook (however the preface says "The length of a little over four hundred pages is not intimidating to students" ) This is probably a little more than you want to learn for your project, but probably about the minimum you'd need for a reasonable analysis of a bridge. I believe that the usual way to to determine how much a balsa bridge can hold is empirically. One builds a model using ones best guesses, loads it until it fails and tries to learn where improvement is needed. This may require careful observation since failure may be sudden. Using information obtained for the experiment one repeats the process until one is satisfied one has a good design or runs out of time or materials, then one recreates the best performing design for the final product. I suspect using one of the online simulators to get a rough idea, then experimenting with physical models will probably be more productive than a mathematical analysis, particularly considering the variables involved with a material like balsa and type of joints you'll likely be using.
8th Grade Schedule?! Help Choosing Courses?
I would recommend taking the more challenging classes: Algebra 1 Physical Science Language Arts Social Studies (Seminar) And here's why. Four years from now, you'll be applying to colleges. And the colleges will be looking not only at your grades, but at the type of classes you took in high school. They want students who have challenged themselves with the most difficult courses their school offers... the honors and AP classes. They understand that those classes are harder, and they take that into consideration: they'd much rather see a few Bs in harder classes, than straight As in regular classes. So once you start high school, you'll want to take as many honors and AP classes as you can handle. Now, colleges won't be looking at your grades and classes from middle school. However, taking these harder classes in 8th grade will prepare you for the more difficult ones you'll take in high school. This will also give you a chance to see how well you can handle a full load of advanced classes... sort of a test run. If you do well in them, you'll be comfortable taking the harder classes in high school. But if it turns out to be too much and your grades aren't so great, you'll know to cut back a bit... and since colleges won't see your grades from 8th grade, it won't matter if they aren't all As! My daughter is a cheerleader, too, and also a gymnast and track athlete. She took all the hardest classes all through middle school and high school, and she was able to handle it. It was a lot of work, and there were times when she didn't get much sleep, but it definitely paid off... she's been accepted to some really great colleges! She plans to study pre-med, and cheer in college! Good luck!
Should I choose mechanical or civil engineering?
First of all, you can not compare apple with mangoes. Because both branches are different. It`s up to your interests are. In my opinion, the biggest overall difference between Civil and Mechanical branch is as simple as static and dynamic. Generally civil engineers works on things which are static in nature e.g. bridges, roads,buildings etc. On the the other hand mechanical engineers works on dynamic i.e. moving things e.g. engine,turbine,bearing,operations in a production unit etc.But still if you want to compare you can based on different parameters.Job and money - The initial years for a civil as well mechanical engineers are struggling ones. As you move up the ladder it gets better. From my personal experience I think civil engineers gets paid more than their mechanical counterparts. This happens because the project related to civil engineers are more costly than mechanical. The big one plus point about civil engineering is the number of post in government. Central as well as state governments have plenty of openings compared to mechanical or any other branch. Note that I said compared to other branches. It does not mean that there are lots of openings so that you could get a job easily. Competition for government jobs can`t be underestimated. Research and then think.Satisfaction - It depends on personal thinking. But the life of civil engineer is spent mostly at construction site. This is obvious because after a structure gets built there is no work remaining for them. So be ready to work under sunlight, dust, helmet on your head, dealing with contractors, remote sites away from city. You will not get to enjoy day to day corporate life as experienced by IT people. On other hand, being a mechanical engineer you have lot of options to work in. Right from IT company to construction company to heavy machinery builders. So indirectly you have options to choose from.
What is shear force and bending moment and why do we need to calculate them?
Shear force is the internal force on a member when the force is not applied at the axis. Shearing force is the force divided by the cross-sectional area.Bending moment is the force trying to rotate the member. Moment is the perpendicular distance from the force to the axis multiplied by the force.To better understand the two terms, consider the following 2 examples:Get a piece of spaghetti & hold it in your hands with your thumbs touching each other. Now push your right hand forward & pull your left hand backward. You just sheared the spaghetti.Get another piece of spaghetti & hold it in your hands with your thumbs as far apart as possible but pointing at each other. Now rotate your right wrist clockwise & your left wrist anti clockwise. You just broke the spaghetti in bending.Another example..Get a block pencil eraser. With a blade or a sharp knife put a shallow cut on the top wide edge. Now hold it between your thumb & forefinger & then squeeze bending it up. Here you’ll note that the cut pulls apart. That is because the bending put the top edge in tension.Now put a cut on the downside. Hold it between thumb & forefinger & squeeze it again. Here you'll note that the cut does not pull apart but is pressed together. That is because the bending put the bottom in compression.This is an important fact about the design of beams. Beams carry bending loads. Bending is carried by putting the top of the beam in tension (assuming load is acting downward) & the bottom of the beam in compression. That is why the beams are I or T or H shaped to put the maximum material where the stress will be. As we move towards the center of the cross section of the beam, the fibers of the material above the center are in tension & those below are in compression. This means just like your hands in the shear example above, the fibers at the center are moving in opposite directions. This causes the maximum shear to occur at the center or neutral axis of the beam.Generally, beams fail in bending & not shearing. This is the reason the center of the beams are made thin. For design purpose of beams the analysis of shear force & bending moment induced are of most importance. Both the shear force & bending moment are induced in beam in order to balance external load acting on it.
Why is electrical engineering so hard and complex?
For me, education is establishing a connection between these three things:what you learn, what you do and what you experience in the real worldThis is where things get messy for an average person if he tries to assimilate Electrical Engineering.For eg. I can understand the concepts of ‘State-Space Analysis’ very well in class. I can apply those concepts in Simulink MATLAB to get a clearer picture. However, to understand, how it really affects me in the Real life would require supernatural talent.(PS- Electrical Engineers very well know what I’m talking about)It has taken some of the greatest minds in human history to compile the secrets of Electricity in a form that is understandable to the common mind.Farday, Ohm, Ampere and Tesla have been a species apart from the rest.In line, there’s the challenge of visualizing things.If a mechanical engineer wants to design a gearbox, a civil engineer wants to bridge a river, he/she can very well visualize it. Mathematics follows easily, once you visualize your creation.Whereas, for an electrical engineer, it is an entirely opposite scenario. If he/she wants to calculate the effect of magnetic interference caused by a current carrying conductor on a telephone circuit, there’s just no way to visualize it! You only have hardcore mathematical techniques as your savior!We first do the math, and then find if at all there’s any possibility to visualize.If you can conceive your creations before hand, you can be a great electrical engineer. Tesla always first conceived his ideas in his mind!Electrical engineering is not a place for those who’ve detested Mathematics for their lives! Laplace, Fourier and Z transforms! They have an immense power to transform your lives as well if you get them clearly!Fear of mathematics makes people conceive electrical engineering as complex and hard.Moreover, electrical engineering is a very vast domain. Power engineering, communication engineering, control system engineering and many more are subsets of electrical engineering, intertwined inseparably with each other.What is vast and interlinked is always complex!With all this said, it an awesome discipline of engineering!I hope I’ve answered you.