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Hi everyone. First of all, I apologize for my prolonged absence. A lot of you on here probably do not even remember me, or signed up after I stopped coming here. I must admit I had forgotten about Hatrack in the events that had taken place in my life. Things are wonderful and have been wonderful for a while now-- though incredibly busy.
I am living in Elbtal, Germany now, on a career-based scholarship. I am studying the German language as well as photography; I am moving back to America near the end of June, and I have been living in Germany for a little over five months now. (www.nacelopendoor.org --I am part of the CBYX program).
Now, on to my question. I used to be incredibly into science, and there was a time when I would have been able to figure out the answer to this myself, but my mind is so crammed full of new things that such a simple question makes my mind spin. Hah.
My example: There is a fly in a parked bus, flying around in small circles (because I don't think flies can hover) right above the floor of the bus. The bus suddenly drives forward; does the fly move back relative to the floor of the bus, or does it stay in its relative position, flying around in little circles?
My second question is exactly the same, except in an open vehicle; we'll say an open bus, I guess. Just a bus with no roof and somewhat lower walls. Would the effect be the same, or would it be different because the area is not completely enclosed?
These seem like such irrelevant questions and they certainly should not be as perplexing as they seem to me; I assume it is because I have been so absorbed in learning German lately, that my mind is absolutely fried.
Anyway, thank you a bunch in advance, and I hope all is well with everyone. I will try my best to catch up on any important Hatrack issues, when I have free time.
Posts: 219 | Registered: Jan 2003
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It's not inertia at all really but air resistance that will have the most effect on the fly's motion. A fly has very little mass, so inertial effects will be minimal.
In the closed bus it will continue to fly in the same relative position, almost. There will be a small pull toward the back of the bus while the bus is accelerating but not much.
In the open bus it will be swept away with the air currents.
Posts: 6246 | Registered: Aug 2004
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It would move back on both cases. If the bus or car moves forwards that's a result of a force from the road on the wheels, transmitted to the entire car body. If the fly was sitting on the car itself than the force could be transmitted to it via the fricition between it's feet and the car, but as it is, none of the force that moves the car moves the fly, so the car accelerates forwards and the fly remains still, without any outside force.
[EDIT: Yah, AK's right, with a fly, the air resistance will probably act as a significant force on it, since the air will be moved with the bus, as the air is enclosed in it.]
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The fly will go back along with the rest of the passengers.
If a passenger is holding a helium baloon on a string, however, that baloon will tend to go forward when the everything tends to go backward, because the air (which is heavier than the baloon) is also forced back, and pushes the baloon forward.
Being enclosed doesn't effect anthing as long as you can eliminate the wind.
edit: I forgot that the car was speeding up instead of breaking.
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The fly would be splatted on the window. Cuz that's what happens when flies and humans mix. We're a violent people. Posts: 8355 | Registered: Apr 2003
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Hah, thanks for the quick replies, all. But I am still a little confused... So, assuming that even in the open bus the currents of air coming in from the outside are not strong enough to sweep the fly away: the fly will move back relative to its position over the floor of the bus? But because the air in the bus is being pushed forward with the bus and the mass of the fly is so small, it will stop the fly from going too far back?
Posts: 219 | Registered: Jan 2003
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Another Christine Lavin fan! I didn't know if anyone else would know the song either, but it was one of my favorites a while back, so I had to post it. Posts: 5948 | Registered: Jun 2001
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Thanks everyone for your help. Now I can focus on learning about German and photography, hah. I appreciate it, all!
Posts: 219 | Registered: Jan 2003
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IndexCard!!! Welcome BACK! I remember you very well! I actually thought about you recently, but I don't remember why... anyway, it's good to see you again. Posts: 7877 | Registered: Feb 2003
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Looks like your physics question was already dealt with quite thoroughly (which is good, since I'm currently teaching my physics students about rotational motion, and this is linear motion ).
But I just wanted to say, HI! IC! I totally remember you. I'm glad you are well, and happily busy. Visit every once in a while, 'k? Posts: 32919 | Registered: Mar 2003
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Thanks a bunch for all your help and hellos, everyone. It is good to see you all again, too! =)
Posts: 219 | Registered: Jan 2003
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I remember you very well! I actually thought about you recently, but I don't remember why... anyway, it's good to see you again. ![[Wink]](wink.gif)
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IC! I totally remember you. I'm glad you are well, and happily busy. Visit every once in a while, 'k? 
