Question about a fly?

Burned_Alive · 9 Mar 2006 at 17:23

So, theres this plane on a treadmill......

Scuzi · 9 Mar 2006 at 17:23

WS_TailGunner said:
technically, yes- but a fly is already exerting force on the air in order to stay hovering- the air in the car doesnt move when you pull off, so neither does the fly...same as you sitting on the seat essentially.

But the principles of momentum work relative to 'space' and not the air inside the car.

benjo plz. · 9 Mar 2006 at 17:23

hendrix said:
Ok, how about if you throw a ball in the air (Neglecting air resistance)

In or out of the car?

Exentia · 9 Mar 2006 at 17:25

if you throw a ball horizontally into a cars open rear window and the car accelerates while the ball is still in the air does it land on the backseat or hit the back of the car somewhere?
the answer is it hits the back of the car. Same with the fly...kinda

hendrix · 9 Mar 2006 at 17:25

Phnom_Penh said:
In or out of the car?

Missing my original point here. If you throw it (sitting on top of the car) straight up, fair enough wind resistance will slow its horizontal velocity down slightly, but it's not going to 'Go Bye Byes' as suggested above.

Rich_L · 9 Mar 2006 at 17:25

WS_TailGunner said:
technically, yes- but a fly is already exerting force on the air in order to stay hovering- the air in the car doesnt move when you pull off, so neither does the fly...same as you sitting on the seat essentially.

That's not quite true, when you accelerate the air is compressed towards the back of the car, until acceleration ceases and the air is then re-distributed although the effect isn't really noticeable.

LOL apparently a helium balloon doesn't work for some reason

But the principle is supposedly sound

chopchop · 9 Mar 2006 at 17:28

Scuzi said:
You are making the assumption that the fly has accelerated from a standstill to the speed of the car. Relative to 'space' the fly is travelling at 80mph inside the car and as there is no resistance, the momentum keeps it going. However, if the car accelerated from a standstill with the fly hovering inside, unless the fly accelerates at the same rate as the car, it will splat on the rear.

that wasnt the question. if the car accelerated to 80mph then it would hit the rear screen, albeit not hard and wouldnt kill it. or it may even just be in the rear area of the car if there wasnt sufficient g's to pull it back.

the question was a fly in a car travelling at a constant 80mph, to which i answered correctly.

Scuzi · 9 Mar 2006 at 17:28

Think of a Magic Tree

You have an air freshener/furry dice hanging from your mirror. When you accelerate, they don't remain completely stationary, they lean towards the rear. If it wasn't for the string holding them on, they'd fly out the back of the car. When you are sitting at a constant 80mph, they hang straight down as if you were stationary as there is no acceleration. A fly is exactly the same thing, only it doesn't have a string holding it on.

chopchop said:
the question was a fly in a car travelling at a constant 80mph, to which i answered correctly.

I didn't say you were wrong.

The_TailGunner · 9 Mar 2006 at 17:30

hendrix said:
Ok, how about if you throw a ball in the air (Neglecting air resistance)

nope- ignoring friction (wind resistance) and gravity, inertia will keep the ball going at the same speed...however- if you were to slow down, it would move forwards.

if you only ignore friction, it will drop straight to the floor.

hendrix · 9 Mar 2006 at 17:31

PaulStat said:
Ok so a fly is in flight in a car that is travelling at 80mph, since the fly isn't actually touching the car as such. Does it have to fly 80mph in the same direction to avoid being splatted against the back window?

If the fly magically appears out of no-where, then yes it has to fly at the same velocity as the car.

If the fly was in the car initially seated (seatbelt of course) and decides to fly vertically. Then (neglecting air resistance) no as its moving at the same velocity as car already.

Correct me if i'm wrong of course but shouldn't this be end of conversation? :confused:

benjo plz. · 9 Mar 2006 at 17:31

hendrix said:
Missing my original point here. If you throw it (sitting on top of the car) straight up, fair enough wind resistance will slow its horizontal velocity down slightly, but it's not going to 'Go Bye Byes' as suggested above.

It will slow down, as I said before the extent of which depends on height.

gord · 9 Mar 2006 at 17:32

Burned_Alive said:
So, theres this plane on a treadmill......

Actually

If your travelling at the speed of light on a treadmill and the plane contains a fly, do you have 1 sandwich or 2?

Can. Worms. Explode.

The_TailGunner · 9 Mar 2006 at 17:32

Scuzi said:
a fly is exactly the same thing, only it doesn't have a string holding it on.

ah- there IS a string of sorts- the fly is exerting a force on the air in order to "hover"

chopchop · 9 Mar 2006 at 17:32

hendrix said:
Lets say you are standing on top of a car thats travelling at 30mph. You jump vertically. Do you 'fly' backwards???

No!

?? what has that got to do with my answer???

i know what would happen to a person that was stood on a car. it is infact blatently obvious to anyone. think motorbike rider.

chopchop · 9 Mar 2006 at 17:33

Scuzi said:
I didn't say you were wrong.

but you posed a completely different question to the one i answered. :confused:

hendrix · 9 Mar 2006 at 17:33

Phnom_Penh said:
It will slow down, as I said before the extent of which depends on height.

Err, wrong.

Its Horizontal Motion has nothing to do with its height, gravity has no effect on its horizontal motion!!

Rich_L · 9 Mar 2006 at 17:34

gord said:
Actually

If your travelling at the speed of light on a treadmill and the plane contains a fly, do you have 1 sandwich or 2?

Can. Worms. Explode.

What if the fly turned on the torch it was holding as well?

Scuzi · 9 Mar 2006 at 17:35

WS_TailGunner said:
ah- there IS a string of sorts- the fly is exerting a force on the air in order to "hover"

AARRGGHH!!

The air resistance which would cause a 'string effect' is negligible and as far as this case is concerned, irrelevant. The fly is free to move anywhere in the car unlike the object on a string which has a fixed range of movement.

chopchop said:
but you posed a completely different question to the one i answered.

The discussion has progressed from the original question to the effects of acceleration. I wasn't correcting your explanation, I was clarifying a point in order not to confuse the acceleration issue.

hendrix · 9 Mar 2006 at 17:36

chopchop said:
?? what has that got to do with my answer???

i know what would happen to a person that was stood on a car. it is infact blatently obvious to anyone. think motorbike rider.

And its blatently obvious to anyone with an understanding of newtons laws of motion that "An object will remain stationery or continue moving at constant velocity, unless acted on by an external force"

Wind resistance would slow it down yeah, but its not going to bring the fly to a complete stop in mid air is it?

happytechie · 9 Mar 2006 at 17:38

If we have rationalised that problem out consider this:

a car is traveling at 80mph, it hits a fly that's flying at 20mph in the other direction over the road. Obviously the fly is toast but it must accelerate from 20mph to 80mph in the other direction. at some point for a brief moment it will be stationary, and in contact with the windscreen of the car. Can I conclude from this that the car's windscreen is also stationary for a brief moment?

Answers in no more than 200 words please.

HT