Dave

Same here. I've gotten better though, but my thumb sometimes just refuses to move very much unless I move it in such a way as to crack it (I don't mean pulling it back or whatever, but if I twist it in a certain way, it cracks and becomes normal again).

I've learnt that I suck at tetris, badly. Which is a bit stupid considering, being an undergrad mathematician, I can't tesselate shapes

I ain't gonna argue, I've no qualifications in Biology. Apart from GCSE, and that was pretty useless, although we did do a little bit of biology. I assume it's still pretty harmful for humans though?

Try phrasing it this way. Since the guy obviously believes in gravity, liken the situation you're talking about to a man jumping out of a plane, with a parachute. Point out the simple fact that when the guy pulls the rip cord, he doesn't continue accelerating and die in a mess on the floor Either that or just beat it into him

Probably needs longer to be honest with you. I'd say that there's probably a number of factors involved in bacteria reproduction, and although I'm not a biologist, I'd probably give it a bit more time.

Nice crystals - I suggest you read up on the back of the bottle of hair spray to see what's in it before trying to stiffen the crystals with it though.

The can crusher sounds the best so far - although the first time I read it, I thought you said car crusher The most impressive levitation you can get is a superconductor. This is mainly because you need liquid nitrogen to cool the metal/ceramic down to a point where it superconducts - this is often in the region of around about 10-20K for metals, higher for ceramics - and hence you get lots of nitrogen vapour coming from it. Not suggested for a science fair project though

I should imagine E.coli would be a rather dangerous bacteria to cultivate myself.

Yeah. Co-incidentally, my gf lives in Plymouth. Not that anyone could possibly be interested in that, but hey Oh, and good look with the A-levels, Chemistry can be quite hard, but it's worth it in the end.

When you're dealing with constant acceleration, there's one very important equation, and that is obtained from a velocity-time diagram. As you may know, the displacement travelled can be worked out from one of these diagrams by calculating the area under the graph, so for the simple case of constant acceleration, we get a trapezoid shape (trapesium). Assuming we start off at an initial speed u and end up at a final velocity v in a time t, then the area which is the same as the displacement, s = t*(v+u)/2. You also know that a = (v-u)/t. Now by using these two equations, you can derive the rest of the uvast equations - by re-arranging the second one, we have v = u + at. Then by substituting for v into the first equation, we have s = ut + 0.5*a*t^2. To get the one we want, we need to eliminate the variable t (time), so by rearranging the second equation, we get that t = (v-u)/a, so by substituting into the first equation, we have s = (v-u)(v+u)/(2s), which implies that v^2 - u^2 = 2as, and hence v^2 = u^2 + 2as as required. Basically, all I'm trying to say that the only one that has a direct link to some physical interpretation is our original first and second equations. The other equations are literally the same equations, but with different variables missing each time. They only aid us in obtaining numerical solutions to problems with constant accelleration. Hope this helps.

Don't think so, we're just getting traffic through it (I think).

bah, business (congrats btw )

First off, 1/0 is not infinite. Division by zero is an undefined operation. I've explained this in another thread, so I'm going to try and clear this up once and for all. Let's say you want to divide one number by another. What does this actually mean? In a real world context, division is finding out how much of a cake you can share equally between 3 people, for example. Say you want to define the division operation in a more mathematical way. So say we have some fraction a/b, where the / defines the division operator. The fraction a/b basically says "find a number so that when you multiply b by that number, the answer is a". In other words, find a number x such that b*x = a. (Then x=a/b.) So for the case 6/3, x is obviously 2. Now lets consider what we get when we consider 1/0. If we want to keep things consistant, it makes sense to use the same definition for division. So let's bung the numbers in: We want to find a number such that 0*x = 1. But just look at this for a second - if you multiply any number by 0, then you're going to get 0. It's impossible to find a number that satisfies the equation 0*x = 1, so 1/0 must be undefined. Now to the other bit. There is a great temptation in mathematics (as you have done) to toss around things like infinity casually in equations. The problem arises when you consider that when you say "infinity", it's not actually a number, but rather a symbol to describe an idea. Things like 1/infinity = 0 are really shorthand for a more complex method of saying that the limit of 1/x as x tends to infinity is zero. This is basically saying what you said; if you take a sequence of numbers that goes 1, 1/2, 1/3, 1/4,... and carry this on forever, then the sequence of numbers will tend to zero. What your friend said is wrong, quite frankly. If you take any real number, say a, then apply the same principles - consider the sequence of numbers a/1, a/2, a/3,...,a/x,... Then we have that the nth term of the sequence is actually equal to a*(1/n). Now as you increase n to an extremely large value, 1/n is going to tend towards zero. As I said before, any number multiplied by zero is equal to zero, and since a is constant, the limit of the sequence in this case will be 0. I hope this helps some, it's a bit mathematically orientated, but to explain it properly you need to grasp the concept of limits and sequences of numbers tending to certain values. Cheers.

Indeed.

I got to 2800 but it didn't register my score

Like skye said, thrust is the force pushing the plane through the air, which comes from the propeller or jet engine on the plane. Drag is effectively the air resistance from the plane travelling through the air. (this is quite a basic description)

All radioactive materials tend to decay towards lead because lead has the largest binding energy per nucleon (I think - we did it in A-level physics and it's been at least 8 months since I looked at the curve )

Right.

Go have a look at http://www.ticalc.org/ as it has a few tutorials and lots of programs.

Proof by contradiction isn't something you can just learn overnight really. You need to be able to manipulate the statement and make an argument where the end result contradicts your first statement, and in a lot of cases, this is quite hard. I've come to see that contradictions are often used for quite short proofs most of the time, and they provide a quick and easy way to prove statements that are not as approachable by a direct method. This isn't the case for all contradictive proofs though, as obviously quite a few are long winded. I suggest when you look through a proof that uses a contradiction, look at the way the statement goes through one logical step to another and see how the statement is being manipulated. I think it's one of the hardest methods of proof to learn, because mainly you learn completely by example. Hope this helps in some way.

It's a car. This is better than no car at all.

Chopper challenge rules all

Oops.

I'm still an unknown quantity Oh wait..

You're getting a new car. I'm getting an old 1996 fiesta. Enough said.