Uber-Dan

Hey all, So I'm doing an assignment on swimsuits and their effect on performance, and I decided to make one of the factors I consider buoyancy. This was because numerous sites talked about how buoyancy is vital, and how FINA has even imposed regulations on it to keep the playing field fair. They say that this is achieved by using lighter foam-like materials, for example polyurethane, to increase buoyancy, but there's one problem. After some extra research, I can find no articles that say that buoyancy is depended on the object's weight or density at all. Buoyancy appears to be a single force that pushes upwards, and is dependent on the object's volume, the liquid's density and the force of gravity, and not the object's weight. What I think has happened is that the articles have misused the word buoyancy, instead of net upward force (or its equivalent), as the object's weight only seems to comes into play when you balance its weight in newtons against the buoyant force and come up with its net upward force. So in essence, my question is this. Are all of the websites wrong, or do I just have a incomplete definition of buoyancy? If so, could you point me to a reliable source which holds the correct one? And I also wanted to make sure that there isn't another word for an object's net upward force in water, as that would be cumbersome to say all of the time in my report. Thanks in advance, Dan

Hey all, I am doing a research assignment in Physics on whether swimming with a woollen swimsuit, swimming bare-chested, or swimming in an LZR Racer swimsuit makes results in faster swimming. I have found all of the theoretical information that I need, to do with the physics behind it, but I can't seem to find any journals or reports that talk on the difference swimsuit material makes on swimming speed, that is, that have done experiments and gained tangible data. I can do without it, but as my report would be better with it, I thought I'd check if anyone knew of any such reports, experiments etc that I could checkout on the subject. All I have right now is that the LZR racer swimsuit should be faster according to the physics, but apart from Olympic records set using the suits, I have nothing definitive that says that it has been tested and is faster. Feel free to ask if you need clarification or have any questions, but other than that, thanks in advance.

Hello all, I’m not sure whether to put this in the physics or chemistry section, so here goes. I have been conducting an experiment consisting of running 6 volts of electricity through an electrolytic cell made up of two steel electrodes submerged in salt water, and then measuring the amperage generated. I would then change the concentration of salt in the solution and test it again. So the first test was with 0.5g/100ml, then 1g/100ml etc. My question resolves interpretating the results. The averages of the results were as follows: 0.5g/100ml = 0.147A : Uncertainty % = 3.409% 1g/100ml = 0.237A : Uncertainty % = 4.225% 1.5g/100ml = 0.290A : Uncertainty % = 1.724% 2g/100ml = 0.333A : Uncertainty % = 1.500% 2.5g/100ml = 0.363A : Uncertainty % = 4.128% The experiment was conducted in a test tube with fairly close electrodes. My question is, why do the results create an exponential curve and not form a linear relationship between the concentration of solute and the amperage generated? I can only assume it is something to do with the voltage not being that high, or that some other chemical reaction is taking place more often when the ion concentration has gone up. I’m really not sure, so what are your thoughts? Regards, Dan

But apart from those two, do the other ones I mentioned work?

Here is my attempt at summarising the experiment based on the above responses and extra research. So, correct me where I go wrong, the equations go as follows: At the cathode: 2H2O(l) + 2e-—> H2(g) + 2OH-(aq) The hydroxide is then attracted to the anode and moves there. At the anode: 2Cl-(aq) —> 2Cl2(g) + 2e- (Only where it reacts with an alloying element) 3Cl-(g) + Fe(s) —> FeCl3(aq) + 3e- (More common than the straight chlorine reaction) FeCl3(aq) + 3OH-(aq) —> FeOH3(s) + 3Cl-(aq) Fe3(s) + 6OH-(aq) —> Fe2O3(s) + 3H2O(l) (I am almost 100% sure this is wrong, but I would like to know if anything similar to this happens, and if so, what is the exact reaction?) In the solution in general: Na+(aq) + OH-(aq) —> NaOH(aq) This is likely riddled with issues and is also probably missing some parts, so I would appreciate it if you could point them out.

If it helps at all, the electrodes were stainless steel (I think that adds in chromium or something) Also, as for the colours, because of the method we had to follow (because it is an assignment), we could only have the power on for around 5 seconds, and even then we could only use 6 volts and it had to be done in a test tube. This was to try and protect the school-owned electrodes from unnecesary harm, but due to that, measuring the colours was a bit difficult. Some of my friends who are doing the same assignment, however, aparently left their’s on too long and the top part of the water near the electrodes (unsure if it was around the anode or the cathode), turned a yellow-ish colour. Hope that helps.

Thanks for the response. My only problem is that when I conducted the experiment, there was a small amount of chlorine gas produced. I'm guessing this is because the iron wasn't pure, and had carbon (and quite possibly other impurities) added to make it into steel. What do you think?

Hello all, I have been working on an assignment based on the electrolysis of salt water using steel electrodes, and I have hit a research block. I am finding it hard to find out what happens to the steel electrodes during the reaction. I know that a small portion of the water separates into H2 and 2OH- at the cathode, that the chlorine ions turn into a gas at the anode, and that some sodium hydroxide is produced (please correct me if any of this is wrong or if I have missed anything), but I am not sure what happens to the steel. I’m assuming that it dissolves from the anode and gets deposited on the cathode as rust, but I can’t find any research to support this (or really any other) hypothesis. If anyone could help me find the correct reactions in relation to the steel or even the other reactions, that would be greatly appreciated. Regards, Dan