Physics Lab B/C

[StampingKid]

And to answer the question as asked, I recall alot of teams getting similar scores last year and think I have read of similar scores this year but there has always been that caveat that a score will necessarily vary from set up to set up.

[Flavorflav]

Nejanimb,
We built the single bladed turbine for test purposes only, and if you read my previous post it
performed better then an equivalent size 2 bladed turbine. There is more to it then mass! Last
year we were worried that it wouldn't "self start". Remember there was no minimum diameter
rule last year. This year we were worried about how they would inforce the diameter "rule"?
Sounds like you had a neat setup at your regional. Good luck.
Greg Doe
Smyrna, TN

It's hard to argue with empirical data, but the one-blade assembly doesn't make sense to me, either. It seems to me that the counterweight should increase your inertia while supplying no additional rotational force, and so replacing the counterweight with any type of blade which produces more in the way of rotation than it sucks in the form of inertia should be an improvement.

[fleet130]

the one-blade assembly doesn't make sense to me

Using only one blade reduces the air resistance of the turbine, making it easier to turn. Since air resistance is non-linear, a small reduction in skin friction may produce a large increase in speed (and therefore voltage). On the other hand, the increase in friction caused by more mass is relatively small.

I would expect changes in speed/voltage due to difference in inertia to be very small. It should just take longer for the turbine to accelerate to maximum speed. Much of the observed difference can be attributed to additional friction in the generator/motor bearings caused by the additional mass.

[blue cobra]

I got a combined voltage of, probably ~1.25V. Apparently this was good, because I guessed on nearly every question on the test and didn't even bother to do the equations for heat transfer and got 1st

[Greg Doe]

Blue cobra
Good job! When you win with a poor performance it's still sweet. When you finish second or
lower, you always wish you had done a little better. Was this your regional, or state event?
Greg Doe
Smyrna, TN

[blue cobra]

Thanks, it was my Regionals.
I figured there was no way I medaled, so they had to call my name a few times before I realized I did

I'll have to actually study for States

[Melkor6000]

Thanks, it was my Regionals.
I figured there was no way I medaled, so they had to call my name a few times before I realized I did

I'll have to actually study for States

Been there, it's kind of exhilerating, isn't it? And then of course I got thrown in for states, too, which was never much fun

Anyway, could someone briefly idiot-check a possible design here?

CD center, half inch outside the hole or so. Glue on toothpick (minus tips), attach blade from 2-liter bottle. glue on small straw on the other side. Fill straw with play-doh or something similar until it balances. Since play-doh is more dense than plastic, you won't need very much to counterbalance (maybe an inch or so of the straw filled). cap outside end.

Think this will work?

[evbassboy13]

Anyway, could someone briefly idiot-check a possible design here?

CD center, half inch outside the hole or so. Glue on toothpick (minus tips), attach blade from 2-liter bottle. glue on small straw on the other side. Fill straw with play-doh or something similar until it balances. Since play-doh is more dense than plastic, you won't need very much to counterbalance (maybe an inch or so of the straw filled). cap outside end.

Think this will work?

I don't see why not. I doubt you'll need to fill an inch of the straw, but the idea sounds pretty solid. You'll have to make sure you have a solid cap on there just in case, but I doubt it'll fly off.

[EastStroudsburg13]

I got a combined voltage of, probably ~1.25V. Apparently this was good, because I guessed on nearly every question on the test and didn't even bother to do the equations for heat transfer and got 1st

That exact same thing happened to me except I got worse on the voltage and maybe a nit better on the test but not as much. We figured everyong else must have failed on the test pretty badly.

We had a combined voltage of about maybe 650-700 mV or so at regionals, but we wound up placing third. I'm guessing that the majority of that came on the test portion, but isn't it slightly unusual for a voltage this low to place so high?

[SSANationalTeam1]

yeah, at our last invitational, we got 1 question right on the test and still got 4th