Shape of a raindrop- EPQ

Is the title' What is the shape of a raindrop' sufficient for an EPQ? I was thinking of doing this by making a wind tunnel and then putting drops of water in it and imaging it. I could then go on to explain why the raindrop is shaped that way (surface tension etc etc). Has anyone hear of/ done this experiment before? How hard is it to get the wind speed just right to make raindrops hover in the air (my research tells me that large raindrops fall at 9 m/s)? Do normal fans even blow air at that speed or would i have to make one? Does this require too much trial and error? How should I tackle doing something like this?

Please help!

Reply 1

Tortious

Original post by 22flowerpower22

I think this is a little too ambitious for an EPQ, and bear in mind too that you'd need to write a fair amount on it.

I did my A2 Physics coursework on optimising a Gaussian gun and found that difficult enough since I didn't really understand the complex physics behind it and how the different factors (number of ball bearings/magnets etc.) were linked, so I "muddled through" most of it - I felt very out of my depth and it wasn't an enjoyable experience. I'd be inclined to pick an experiment based on more "traditional" apparatus (trolley down an inclined plane, perhaps?) since you'll find you have more to talk about.

Reply 2

tehforum

puhep1.princeton.edu/~mcdonald/JEMcDonald/mcdonald_sa_190_2_64_54.pdf

Reply 3

22flowerpower22

Original post by Tortious

What if I changed the experiment to determining the speed at which raindrops fall (which will require simpler physics)? Is the writing about this experiment what makes it ambitious or the set up?

Reply 4

Tortious

Original post by 22flowerpower22

What if I changed the experiment to determining the speed at which raindrops fall (which will require simpler physics)? Is the writing about this experiment what makes it ambitious or the set up?

I think it's the setup - but changing your experiment to the above won't really help because the answer's fairly simple.

Within a certain distance from the Earth's surface, the strength of its gravitational field is 9.8N. In short, if you ignore air resistance (which I'd argue is going to be tiny on a raindrop anyway - or at least sufficiently small not to vary much between different sizes of raindrop), objects dropped in a vacuum fall at the same rate, so "big" and "little" raindrops should hit the ground at the same time. You can prove this by rearranging the equations, but it's been too long since I did this for me to remember how to do it myself. Instead, I'll refer you to these answers - the bottom one explains it particularly well.

Reply 5

mathperson

Yeah too ambitious, you should change to something easier.

Spoiler

Reply 6

username969261

Original post by 22flowerpower22

What if I changed the experiment to determining the speed at which raindrops fall (which will require simpler physics)? Is the writing about this experiment what makes it ambitious or the set up?

Umm, a raindrop is attracted to the earth by gravity, it will fall at that speed, 9.81m/s - a small amount of resistance from the air, but, since its so small, and your calculations so approximate, you may as well cancel out the air resistance, call it negligble.

you would be using a f/m = a, or s=d/t, and then maybe f=GMm/r^2 ..

There is nothing new here. And you certainly cant write 5000 words on it.
You could do something about Newton though, a history of him, and how he formulated all his stuff. But not just the speed at which an object with mass moves to the earth.

Reply 7

22flowerpower22

Original post by beaver_tron

If I do an experiment/ make something I only have to write 1000-2000 word report on it. So the experiment has to be of a sufficient difficulty.

Reply 8

username969261

Original post by 22flowerpower22

If I do an experiment/ make something I only have to write 1000-2000 word report on it. So the experiment has to be of a sufficient difficulty.

I see, so you could focus on something like simple harmonic motion? It would be fairly easy to cover.It is covered in A2 spec, so borrow a textbook and do some reading.

You could then do three experiments and analyse each for their SHM qualities ? .. if they match the definition or not, if not, why do they not? - Not sure of the difficulty this would be graded as however.

Not sure if you can pull the raindrop one though, its to simple, one, to experiment, and two, to explain.

My epq was an essay only, so i cant really give any inspiration from my experience.