The Thing

Haha I figured out the answer right after I thought of how to explain that the radius equals 340 to you. So let's start with 340 then get to my solution. 340 is derived from the fact that if you draw a line from the center of the semicircle to the point R, you will get a right angle triangle. The center of the semicircle is also the center of side PS for the rectangle, thus you will get a right angle triangle with sides 14 and 12, and by Pythagoras the hypotenuse, or the radius of the circle, is root 340. Mind that the radius of the circle is the same from the center to any point, so from center to point X or Y is root 340, which is why I said it was easy to figure out XP and SY, because you they're then root 340 - 14. But let's ignore that because, like I said, it is not very important. So let's draw a line from the center of the semicircle to the circumference at point U. Now you have yourself another right-angled triangle, namely triangle O(center of the semicircle)UV. You know that the radius, or the hypotenuse of this triangle is root 340. Let's make the side of the square STUV x, and thus the remaining side of that triangle is 14+x. Now we have an equation: sqrt(340)=sqrt(x^2+(14+x)^2) Square both sides to get the quadratic equation 340=x^2+(14+x)^2 Solve.

XP and SY are easily found. The area of the semicircle too. However, to get STUV you need to subtract not only the rectangle but the shape RTU and UVY, and how do you calculate their areas? Is it the last question in the booklet or one from the last section?

SY or XP will not get you the side of the square. XP is the radius of the circle minus 14, so root 340 - 14. But what's more important than that is the length of VY. If you somehow got VY, the problem's solved. By the way, what grade level is this question?

Er...a wild guess: a=-1, b=-4, c=-3 and d=-2? EDIT: OMFG There's a second page...I'm an idiot.

Thank you thank you. That was EXACTLY what I needed BhavinB. And what is a second order nonlinear optical property? It doesn't mean anything to me, but I'd like to know. Incidentally, would you know anything about mechanoluminescence? Why do crystals with impurity defects in lattice also exhibit mechanoluminescence?

Okay, I've done some research. Assymetric crystals are non-centrosymmetric crystals, lacking a center of symmetry. However, I'm having a difficult time visualizing this. More help please? Does it have to be an irregulary looking shape to have no center of symmetry? The problem is I can't figure out how the atoms will be arranged in the crystal lattice if the crystal has a low symmetry. They wouldn't be stacked neatly like, say, in a cubic or hexagonal crystal, would they? Will it have to have defects to achieve low symmetry?

Err...not unless chiral compounds exhibit mechanoluminescent behaviors... This question is one that I had when I was trying to learn about mechanoluminescence, the luminescence of a material from a mechanical stimulus. Only asymmetric crystals exhibit this behavior. So that's my question. What is an asymmetric crystal structure?

I have never really understood what it means. So, what is it? Could anyone provide some info or a link? I've tried googling but haven't found anything.

One scale is enough. First you need to buy a boat. Those wooden 1 person boats that sink very easily. Stand on the boat. Mark how deep the boat went into the water (draw a line). Get out. Start putting rocks (small ones, or at least ones that are less than 5 kilos) in. Put more rocks until the boat sinks to the line you just drew. Weigh all the rocks on scale. Add.

JustStuit got the answer. That was before he edited. Now his answer is just wrong .

Um, what crystal should I use? That's my biggest problem now. What crystal would be good for an experiment like this?

Neodymium magnets are pretty hard to demagnetize. Heating it above its Curie point will, of course, make it lose its magnetism. It's Curie point's quite low - 320 Celsius I think, but it begins to lose magnetism at a much lower temperature. I have no clue as to how much current you need to put through a coil actuator to demagnetize a neodymium magnet, but I suspect that you will need a huge pulse. As for the conventional ways to demagnetize weak magnets, such as banging the ---- out of them using a gigantic hammer, I'm not sure that it will work with neodymium magnets - most likely you'll crack the covering, and send pieces of the magnet flying around like bullets. Then the material inside will corrode. DON'T try it.

When it's wrong. Score.

Thanks calbiterol. It still fires, but is just not satisfactorily powerful. In the future, should I have a series of ball bearings, each smaller than the one behind it? And I blame all my failures on the small sizes of my magnets!!!

Well I'm done my Gauss rifle. It didn't work as well as I would have liked. The ball was slooooooow. It had 10 stages and the exitting ball is so slow that you could stick your hand in its way and feel absolutely nothing and the ball will just slide off your hand. I can barely feel it hitting my hand. And instead of everything happening at once and you hearing an almost uniform loud clink when the thing fires, mine you could track the sounds as it went clink-clink-clink-clink. I am pretty sure that I have optimal spacing - 6cm, as any closer would send the ball hurtling towards the magnet in front of it prematurely. I estimate that I could have placed just one other ball bearing in front of each group of 2 balls. That was my spacing. The ball just made pass my table and fell like a stone. All very fast of course. But I think the reason that why it, well, failed, was because my ball bearings were infinitely bigger than my magnets. They were 3/4" in diameter, while my magnets were 1/2" in diameter and 1/4" thick. So the size wasn't all too ideal. I think that my magnets, however strong the shop advertises, are really not all that strong. Okay, I could open my fridge door with one, but I'm pretty sure they aren't the N48 ultra powerful NIB magnets that everyone else uses. AND they're small, as mentioned. So, is that why it would not go faster? It's actually pretty pathetic, the speed. You don't feel a THING as the ball hits your hand. But the ball at the end is moving, so I guess that's something... Incidentally, I've increased the speed of the last ball by using a smaller bearing. It's still very slow though. It travelled like maybe 30 or 40 cm before dropping like a stone. I'm pretty sure it could have rolled much further if I let it roll on the table instead of firing it at the edge of the table though .

I got ze bearings! Got an entire jar of them now . I'm thinking of a launching mechanism for the Gauss Rifle, one that I can control from a distance through a wire. I'm thinking of an electromagnet controlling a little "gate" which blocks the first ball, and when I press the switch the gate is attracted upwards, letting the ball roll to the first magnet. However, are there ay other ways to create a launching mechanism? Thanks a lot!

Err... I'm on the other side of the country . Vancouver.

The thing is, I'm not in the States. I'm in Canada, and the Radio Shack is The Source by Circuit City here. I'm pretty sure they don't have reed switches, but I'll try to get one. Any other ideas?

Thanks. However, are my magnets too small? They're half an inch in diameter. How about a reed switch motor? Maybe I'll build one of those and control its speed with another magnet. It's extremely simple to build. Now, I'll just have to find a reed switch and I don't think Radio Shack has one...

As the title says: What can I do with 20 strong 1/2" disc magnets? I'm thinking of building something, but what? (except a Gauss Rifle). The project can use the magnets, and electronic parts and a 9V battery. It's for a school project. Thanks.

Well, that's the problem. I can't find steel balls anywhere. I've asked for everything: steel balls, ball bearings, steel marbles, steel BBs, steel pellets, you name it. I've went to every shop I can find - hardware shops, Home Depot, craft shops, auto parts shops... Basically, I can't find a sphere that is made of metal. . I have one last resort: my teachers. Going to ask them tomorrow. Incidentally, yesterday I built a very crude coin launcher on my dining table. I had 3 stages only, but it worked, and the penny was launched off the table. It wasn't very far - think it was 5 inches. But I used coins lying flat on the table, and obviously it was very crudely done - did it in about a minute.

Record's 42195 digits. A Janpanese, Hiroyuki Goto memorized it.

Thanks Caver. I'll try to make this stuff in my school's chem lab on monday. 5614, I thought once ferrofluid gets onto a strong NIB magnet, its nearly impossible to get it off?

Okay, I've met a problem that I never thought I'd run into: I don't have any ball bearings!!!!11!1 What can I use to substitute for the ball bearings? EDIT: I'm going to an automotive parts shop tomorrow to look for ball bearings. But, to prepare for the worst case scenario, what can I replace them with in my gauss rifle?

I memorized the 35 digits Ludolph van Ceulen calculated. I remembered them since I was about 8 and never forgot them . Now I think I can memorize about 8 more digits, that's it. I would memorize it in groups of 4: So, first it's 3.1415926 - calculated by the Chinese mathematician, then it's groups of 4: 5358, 9793, 2384, 6264, 3383, 2795, 0288, 4197....