# Fly in a car problem

uzless
Posers and Puzzles 18 Oct '06 18:32
1. uzless
The So Fist
18 Oct '06 18:32
A fly is resting on the passenger seat as you are driving down the highway at 100km/hr. If the fly jumped off the seat, then in order for the fly to remain in same spot above the seat, could it just hover or would it have to fly at 100km/hr?
2. 18 Oct '06 18:43
Originally posted by uzless
A fly is resting on the passenger seat as you are driving down the highway at 100km/hr. If the fly jumped off the seat, then in order for the fly to remain in same spot above the seat, could it just hover or would it have to fly at 100km/hr?
You mean with the side windows shut?
3. PBE6
Bananarama
18 Oct '06 18:48
Originally posted by uzless
A fly is resting on the passenger seat as you are driving down the highway at 100km/hr. If the fly jumped off the seat, then in order for the fly to remain in same spot above the seat, could it just hover or would it have to fly at 100km/hr?
The fly could just hover relative to the car seat. An observer standing on the side of the highway would see the fly moving at 100 km/hr though.
4. uzless
The So Fist
18 Oct '06 19:42
Originally posted by FabianFnas
You mean with the side windows shut?
Yes, all windows closed. No tricks here, like A/C on etc. Strictly straight up question.
5. uzless
The So Fist
18 Oct '06 19:44
Originally posted by PBE6
The fly could just hover relative to the car seat. An observer standing on the side of the highway would see the fly moving at 100 km/hr though.
This isn't a relativity question. It's a time/velocity question.

And gravity.

Ok, maybe that was too much of a hint.
6. PBE6
Bananarama
18 Oct '06 19:48
Originally posted by uzless
This isn't a relativity question. It's a time/velocity question.

And gravity.

Ok, maybe that was too much of a hint.
Hmm, not sure what you're driving at (...thank you, I'll be here all night...), but if the fly can hover in the same position above, say, a nice juicy piece of poop then it can hover in the same position above the car seat. It wouldn't have to fly forwards to keep pace with the car.
7. uzless
The So Fist
18 Oct '06 19:57
Originally posted by PBE6
It wouldn't have to fly forwards to keep pace with the car.
Then what is keeping the fly's velocity at 100km/hr if it is simply in hover mode?
8. Agerg
The 'edit'or
18 Oct '06 20:02
Originally posted by uzless
Then what is keeping the fly's velocity at 100km/hr if it is simply in hover mode?
hmm...my knowledge of mechanics isn't as good as I want it to be but...

A force has acted on that fly such that it accellerated from whatever speed it was when it entered the car, to the speed of 100km/h when it starts to fly...To maintain that speed, it only needs to counter the opposing forces that would slow it down to carry on *hovering* no?
9. uzless
The So Fist
18 Oct '06 20:04
Originally posted by Agerg
hmm...my knowledge of mechanics isn't as good as I want it to be but...

A force has acted on that fly such that it accellerated from whatever speed it was when it entered the car, to the speed of 100km/h when it starts to fly...To maintain that speed, it only needs to counter the opposing forces that would slow it down to carry on *hovering* no?
10. PBE6
Bananarama
18 Oct '06 20:06
Originally posted by uzless
Then what is keeping the fly's velocity at 100km/hr if it is simply in hover mode?
Another way of looking at it is to ask: what is acting on the fly to change its velocity *from* 100 km/hr? The answer (in our ideal situation) is nothing. In real life, there will be teeny tiny gusts of wind, teeny tiny gravitational effects, teeny tiny electrostatic effects, etc... but they have, as you might have guessed, a teeny tiny effect on the fly.

If the car were accelerating, then you would see the fly change positions relative to the car seat. But since the car is travelling at a uniform speed, the fly will continue to hover above the seat.
11. 18 Oct '06 20:13
It's because the air inside the car is travelling at 100 mph as well. From the flies point of view it is stationary, the car is stationary and the air is stationary so it can just hover.

If the car has no front or back window then the fly will not be able to hover there as the air is not stationary with repect to the car anymore.
12. AThousandYoung
18 Oct '06 20:13
Originally posted by uzless
Then what is keeping the fly's velocity at 100km/hr if it is simply in hover mode?
Inertia.
13. 18 Oct '06 23:39
it's move with the air in the car.

it's like when you jump on a bus you don't move backwards. partly because you're traveling as x Mph when you jump but also because there's no frontal wind resistance os thats traveling at same speed as you.

so thinking about it, it's nothing like the problem you mentioned....ignore me, carry on.
14. 19 Oct '06 12:59
didn't the fly die in the terrible cyclist crash of 06? i don't think flies can hover either.
15. uzless
The So Fist
19 Oct '06 21:172 edits
you are all forgeting about gravity.

This fly is imparting upon itself 0 km/h forward velocity. The car was what got it up to 100km/h. Some of you have implied, (although you may not have realized it) that the air inside the car is somehow pushing the fly. Are you suggesting that after say, a minute, this fly would still be in the exact same position if it just continues to hover?

No one has got it correct yet. ðŸ˜‰