TIL that during WWII, the silk of black widows was used to make crosshairs in guns used by the U.S. Army, as it is stronger than steel or platinum wire of the same thickness.

iDrinkYourShake · 15 days

In the article, it said that they put the spider on a spindle made from a coat hanger, and the spider would try to drop down on a thread, at which point the would start spinning the spindle slowly so the spider keeps trying to drop down while the silk is being wound around the spindle.

AJarOfAlmonds · 15 days

On the bright side, you can be sure that you'll have fresh batteries during the final. I'm sorry about the last test though.

michelk · 16 days

I don't get it. How do you pronounce cement?

danielharkin · 18 days

No, I actually like it. However, I always think of the Zeroth Law of Robotics when I see it.

AlwaysKindaLost · 18 days

I don't know about other people, but tablets aren't a primary computing device. As a college student, I have a laptop as my primary computing device, and a tablet as a more convenient secondary computing device. My computer stays at home, and I take my tablet to all my classes. It can do everything I need in class, while being a lot easier to carry around.

AlwaysKindaLost · 18 days

Can be. Everything on a tablet can be free as well. I have yet to pay for a single app on my iPad.

starseed42 · 19 days

In fact, I asked this two months ago in r/DAE.

zero_factorial · 20 days

Yeah, I usually buy my textbooks online. Right now, I need to buy a workbook for one of my classes. Online prices are the same, so I figured it would be safer (to get the right one and make sure it hasn't been used) to just buy it in store. If they don't get the books in time, I'll have to buy online and ship overseas.

cakedestroyer · 21 days

Of course, treadmills aren't ideal in reality, so there will differences in the way you interact with the running surface.

Another issue I had with Ham 31337's expanation is his statement that:

The key function of the leg muscles during treadmill running is not to produce propulsive forces but to re-position the legs so as to keep the centre of mass stable.

If your legs didn't produce propulsive forces, you would be propelled backward by the belt. Equally, when you're running on a track, your legs still have to keep your center of mass stable, because otherwise you'd fall.

I agree that treadmill running is different from track running due to mechanical deficiencies of the treadmill. However, the two senarios are still physically identical.

cakedestroyer · 21 days

Choosing a static Earth as the frame of reference is still completely arbitrary. I could just as easily choose the Moon. Also, slowing down and speeding up aren't necessarily vital components of running. For the purposes of comparison, the runner can easily be assumed to be running at constant speed.

cakedestroyer · 21 days

Let's examine some variations on Case C. There are 2 frames of reference we can take. Either with the runner, or with an observer beside the treadmill. Assume that the belt is longer that a normal belt, to have more distance to work with.

If the bearings have very high friction, such that the belt is immovable, running would propel you forward while the belt is stationary. To the runner, the belt is moving backward while he is running. To the observer, the runner is moving forward while the belt is stationary.
If the bearings have some friction, such that the belt can move, but with some resistance, running would propel you forward while the belt moves backward slowly. To the runner, the belt is still moving backward at the same speed as before. To the observer, the runner isn't moving forward as fast as before, and the belt is moving backward.
If the bearings have no friction, such that the belt moves freely, running would only move the belt backward. To the runner, the belt is still moving backward at the the same speed as before. To the observer, the runner is stationary, while the belt is moving backward.

All three senarios are identical from the runner's frame of reference. They are also identical in terms of the energy expended by the runner. However, they are obviously different from the observer's frame of reference. The senario with high friction is equivalent to Case B, while the senario with no friction is equivalent to Case A. Because it's impossible to have no friction in treadmills, the motor serves to compensate for the friction.

In conclusion, Case A and Case B are identical. The motor on an electric treadmill doesn't help you run. It only compensates for friction in order to keep you stationary.

cakedestroyer · 21 days

The only problem I have with your explaination is that defining whether or not your center of mass is static is completely dependent on your frame of reference. If I were to take my frame of reference with the runner, then the CoM is static in both cases.

cakedestroyer · 21 days

I agree with your viewpoint. Moving 'forward' is completely dependent on the frame of reference. Say you're running on a circular track and I'm standing beside the track. Lets say that the track can actually spin around the center. Initially, the track is stationary, and you run around a few times. At this point, you are obviously running normally on a track. Then the track starts spinning in the opposite direction as you are running, eventually reaching a point where you are stationary relative to me. Now, at this point, the question is are you still running the same?

The only difference between the two points should be air resistance. This study indicates that a 1% treadmill grade approximately makes up for air resistance in terms of the energetic cost of running on a treadmill and on a track. Thus, 'propelling yourself forward' vs 'preventing yourself from falling back' are physically equivalent senarios. Of course, treadmills aren't perfect, so there may be factors that have additional effects. Overall, the only theoretical difference between treadmill running and track running is air resistance.

Sati1984 · 22 days

I have never heard that in my life. Isn't Hoover still one of the larger vacuum manufacturers out there?

pyroxys · 22 days

Georgia Tech does a superscore thing where they combine your best section scores from both ACTs and SATs. They don't have a preference, but you might want to take both to see what you do better on.

For SAT subject tests, GT doesn't care whatsoever. There are two tests (Chemistry and English) for which you can get course credit for if you do well enough, but they give the same credit as AP, so there's no point if you took AP Chem and AP Lang/Lit. However, some schools do require subject tests, so you should check with their admissions office on that.

I took the SAT two times (only reported one score), ACT zero times, and 3 SAT subject tests because some of the schools I was applying to required it. For GT, the only thing that mattered was the SAT.

Zuol · 25 days

If you're having trouble understanding something, just ask someone. Find people who you can ask for help if you need it, like your professor, TA, or a friend who has taken the class already. The biggest problem I had when I was a TA was that students would rarely come see me for help when they needed it.

davidthefat · 28 days

The problem (I think) with studying abroad for engineering majors is the fact that it can be difficult to find classes fit your curriculum. It's probably easier for liberal arts majors. This is also why you should study abroad early on rather than late in your college career, since you'll be taking more general core classes, so it will be easier to transfer credit.

I will actually be studying abroad this summer in France, but it was easier in my case since I'm going to a satellite campus owned by GT, and we have GT professors going over there to teach. However, there are a lot of people who study abroad all over the world. I think you can study abroad at almost any university you want, as long as you can figure out how the credit will transfer.

Of course, language can be an issue. Some universities will offer some classes in English, which would be the best, but isn't that common. Generally, you should choose a place that speaks a language that you know, to make classes and everyday life easier.

Guillam · 28 days

I wouldn't care if you just said that you hate the Chinese government, but you can't just lump in 1.3 billion people with it and say that you hate China. You should know that the media will only report things that will get them views, which is basically all the negative stuff. The average person in China doesn't experience all 'mistreatment' that is reported by the media. This person was an activist. His experiences are nothing like what most people experience.

zero_factorial · 29 days

When I logged on this morning, there didn't seem to be any problems. I checked, and apparently the system rebooted this morning around 1AM. Also, there was a yellow exclamation point beside the monitor in Device Manager yesterday, but it's gone now. Could our IT department have pushed through a driver update that fixed the issue?

Edit: Never mind, it seems as if it's still having problems. Maybe it was fine this morning because it was right after restarting. The video driver is up to date. I updated the monitor driver. I guess I'll just wait and see. If it keeps being really slow, I'll just switch back to VGA.

wenaus · 29 days

Engineering is definitely fun. You'll meet lots of new people, inside and outside your major, who will likely have the same interests as you. It's not that much work, as long as you have good time management, and don't waste all your time on reddit. It's definitely worth it. You'll have a better chance getting a job than non-engineering, and most likely a higher starting salary. Unless you don't actually like engineering, you'll have a good time.

perilus21 · 1 month

I'm somewhat sure this is how to do it. The answer comes out correct.

Thermal efficiency is the the work output divided by the heat input, so you can figure out the heat input.

The heat output is the heat input minus the work output, so you can figure out the heat output.

It says that half of the heat output is passed to the water, so you can determine the heat absorbed by the water.

Given the maximum temperature rise and Cp of water, you can determine the maximum amount of heat to be absorbed per kg of water.

With those last two values, you can now determine the necessary flow rate of water.

Reptilin · 1 month

I'd be dead, but I would say the remaining kids would fall into one of a few categories:

People who can't or won't do anything on their own, and will basically stay where they are.
People who can survive on their own in the short term, but are incapable or unwilling to consider long term plans.
People who can survive on their own, and are capable and willing to plan for long term survival.

Unfortunately, I think that in first-world countries, people of type 1 will be very common, and will most likely die out within weeks. People of type 2 will vastly outnumber people of type 3, and will likely waste their immediate resources. After those resources are gone, people of type 2 will likely form roving groups who will attack others for food. People of type 3 will be most likely to survive and establish a functioning society, assuming they find a safe place to settle before being attacked by people of type 2.

DelayingAdulthood · 1 month

Because people feel the need to justify their choices to themselves. Why would someone choose a field just to go and say that it's an awful field that nobody should go into? I chose engineering, therefore I think it's better than all the other majors. I chose chemical, therefore I think it's better than all the other engineerings. I chose GaTech, therefore I think it's better than all the other schools. Do I go around talking about it? No, but that's a matter of personality. It's only natural that people will think that what they chose is better than what they didn't choose.

stellarecho92 · 1 month

To be honest, I don't know which would work better. We used ethanol because it was what we had. Would methanol burn off faster?

zero_factorial

TROPHY CASE

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