iwfc87 Posted August 3, 2004 Posted August 3, 2004 Hey everyone. I'm currently doing an experiment involving the physic pronciples of the diameter of the splatter of various liquids. I've currently taken readings of the time taken to fall from a range of heights, the diameter of the splattered droplets. Problem is, what physics principles can I really invenstigate/talk about in my report. I know this sounds like I'm asking you to do my home work, but I'm really stuck . I've tried taking photos of a droplet using a video cam, but this is nearly impossible. Well..various physics principles I have come up with is: terminal velocity force analysis intermolecular bonding (Is this really physics? or chem?) Much help would be greatly appreciated!
5614 Posted August 3, 2004 Posted August 3, 2004 what's this for, GCSE, A-levels or uni.? the 3 which u mentioned are all fine, the last one, is a bit more chem. however, include it in your project, it'll go down fine, just maybe dont use it as your main topic, but more as a side topic.... thats what i do, have a main topic, thats good, and some other sides topics, such as intermolecular bonding [in this case] this will norm get you those extra marks! other than that, i cant really think of other things..... force: includes gravity & friction, i suppose!
SurfSciGuy Posted August 3, 2004 Posted August 3, 2004 The best thing would be to change bonding to forces. You can then look at this in an engineering context as well as a chemical one. As far as force go you should probably be looking at Van der Waal's, Hydrogen bonding, Dipole-dipole interactions (both permanent and temporary), and the host of charge-dipole, charge-charge interactions. It is important to consider repulsive effects as well as attractive effects.
pulkit Posted August 3, 2004 Posted August 3, 2004 I would try to relate the surface tension of the liquid somehow to the splatter pattern and size if I were you. if you want to talk about stuff like terminal velocity you need to also measure the diameter of the initial drop, I hope you keep that in mind.
swansont Posted August 3, 2004 Posted August 3, 2004 High-speed photography is neat; a plain ol' video camera won't work. I had a chance to get some milk-splatter pix and balloons in mid-pop at a conference workshop several years ago. You need a really short flash duration to get it to work. Mechanical shutters are just too slow. I imagine the splatter radius depends on drop size because surface tension is, well, a surface effect. You could measure the effect even if you can't explain all of the physics behind it, if you can reliably change the droplet size. You could also add soap to the mix to reduce the surface tension and measure if that has an effect.
pulkit Posted August 3, 2004 Posted August 3, 2004 If you want to mix soap or play around with surface tension, you should have some sort of method to measure the exact surface tension. I used to do it by counting drops, I don't know if there is an instrument that measures surface tension. Another factor that could be taken into account is the surface on which the drop falls and its coefficient of restitution (e).
aommaster Posted August 3, 2004 Posted August 3, 2004 what's this for, GCSE, A-levels or uni Looks much higher than GCSE level. I would think it would be about A-level standard!
SurfSciGuy Posted August 3, 2004 Posted August 3, 2004 I used to do it by counting drops' date=' I don't know if there is an instrument that measures surface tension.[/quote'] I have an engineering search engine's results here . Hope that helps (bit off topic I guess).
5614 Posted August 3, 2004 Posted August 3, 2004 Well..various physics principles I have come up with is: terminal velocity force analysis intermolecular bonding (Is this really physics? or chem?) Much help would be greatly appreciated! im guessing he wants help with the phsics aspects of this' date=' not other things, this is prob physics coursework, project, wtvr you wanna call it? but i might be wrong, im just guessing.... u could also comment on: if wind speed effects it.... [but thats a type of force, which u said u have already thought of'] what happens when the droplets collide what happens when droplets land on different substances, e.g. water / concrete / sponge.... wtvr, just a variety and obviously droplet size
iwfc87 Posted August 4, 2004 Author Posted August 4, 2004 Hey all! These topics are really interesting. Thanks so much for all ure replies. Yeah..I have to type up an experimental investigation report for Year 12(Australia, A-levels UK i think). I really like the idea of finding a relationship between surface tension and diameter of the droplets (Should work well as I'm using a range of liquids of different vicrosities). About the intermolecular force thing, come to think about it, the topic really fits at the borderline where physics and chemistry overlap, so I just thought of talking breifly about it and later in the an attached appendix with more detail. I better get goin starting my research (physics can get so interesting after experimentation, lots of wondering and pondering and learning from research.) Thanks lots, though if anymore do come in mind, please do tell. Cheers.
aommaster Posted August 4, 2004 Posted August 4, 2004 YAY!!!! I got the A-Level part correct! Nearly. You are doing AS level! The starting point of A levels!
iwfc87 Posted August 8, 2004 Author Posted August 8, 2004 I'm back and I'm stumped. Well..what's happened is I was thinking of Van de Waal forces, and as water has Hydrogen-hydrogen bonding, why does it have a larger diameter than that of olive oil or motor oil when dropped from a range of heights? I also learnt that the greater the surface tension, the rounder the droplets would be on departure (at least I think ), but does that mean a smaller volume of liquid leaves as well? Uh oh..I think I'm really lost now. I cannot seem to relate my data with each other. You see, I've known that motor oil has the lowest surface tension than all my other liquids (water, olive oil and dishwashing detergent), but the problem is, it drops the fastest (understandable as it had the least volume/drop and a moderate mass/drop..but also means more KE on impact), has a dispersion van de waal force (weakest..i think), but despite of these, it manages to maintain the smallest droplet diameter. In fact, nearly constant at all heights
pulkit Posted August 8, 2004 Posted August 8, 2004 Drop size depends on surface tension. Its the energy per unit surface area for drop formation. All drops are expected to be spherical to get min surface (thus min energy) for a fixed volume.
iwfc87 Posted August 21, 2004 Author Posted August 21, 2004 This might sounds crazy, but does anyone know the surface tension of concentrated dishwashing detergent?? I've tried Google-ing, but I can't really find anything. And also, how are droplet volumes/sizes affected by surface tension? Thanks.
5614 Posted August 22, 2004 Posted August 22, 2004 well the surface tension doesnt do much to the area, but it does limit it.
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