Question about a fly?

chopchop · 9 Mar 2006 at 17:41

hendrix said:
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?

now your just babbling.

Visage · 9 Mar 2006 at 17:42

happytechie said:
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

No, because a fly is a macroscopic object.

The_TailGunner · 9 Mar 2006 at 17:42

Scuzi said:
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.

the fly IS free to move, however if it is hovering, it is exerting a force upon the stationary air in the car, and so will only move if the air moves...which it doesnt much.

*pokes scuzi and runs*

hendrix · 9 Mar 2006 at 17:43

chopchop said:
now your just babbling.

excuse me?

Newton's First Law: Law of Inertia
"An object at rest or travelling in uniform motion will remain at rest or travelling in uniform motion unless acted upon by a net force."

benjo plz. · 9 Mar 2006 at 17:43

hendrix said:
Err, wrong.

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

Yah I know that, but the longer its in up, the more it decelerates due to loss of momentum, so the slower it goes.

Balls, you said ignore air.

chopchop · 9 Mar 2006 at 17:43

happytechie said:
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

stationary relative to what? the ground ? the windscreen will never be stationary relative to the ground whilst the car is moving. the fly however would be stationary(relative to the ground) just before it goes flat as a pancake on your windscreen.

hendrix · 9 Mar 2006 at 17:46

Phnom_Penh said:
Yah I know that, but the longer its in up, the more it decelerates due to loss of momentum, so the slower it goes.

It doesn't lose momentum as it moves up. Momemtum is always conserved. If momentum is lost, then the loss of momentum has to be transferred to another object. The longer its in the air, its vertical velocity decreases until it gets to 0, and then it begins to fall. Its horiztonal velocity is unchanged.

benjo plz. · 9 Mar 2006 at 17:47

hendrix said:
snippy

yeh, see the edit

.
What about gravity from the sun and the moon?

.

hendrix · 9 Mar 2006 at 17:52

Phnom_Penh said:
yeh, see the edit .
What about gravity from the sun and the moon? .

F = GMm/r^2 :rolleyes:

Force between two objects M and m.

when M is mass of earth and m is our fly.

Force between fly + earth is gonna be a hell of a lot stronger than the force of our fly + sun or moon

//Edit

@ edit

gord · 9 Mar 2006 at 17:52

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

Thats a whole different kettle of high five.

benjo plz. · 9 Mar 2006 at 17:54

hendrix said:
F = GMm/r^2

Force between two objects M and m.

when M is mass of earth and m is our fly.

Force between fly + earth is gonna be a hell of a lot stronger than the force of our fly + sun or moon

We were talking about a ball.... and I meant horizontal rather than vertical.

hendrix · 9 Mar 2006 at 17:56

Phnom_Penh said:
We were talking about a ball.... and I meant horizontal rather than vertical.

Now my head hurts :confused:

I'm going to pub...

Read up on Newtons laws!

http://en.wikipedia.org/wiki/Newtons_law

Kappa · 9 Mar 2006 at 18:13

Lol, its a silly question, just sit in a car and feel what happens when you accellerate, or have a can of coke on the dash and watch it fall off. Just as long as the fly accelerates to 80mph through pushing on a seat or something then at the 80mph, it is no longer accelerating so the fly can do what it likes with no forces on it because of the contained air. Its hard to imagine, but yeah the fly will have to accelerate with the car, but because of the lack wind resistance it is a LOT easier for it to. But it will look stationary inside the car if it accelerates at the same rate.

Cybermyk · 9 Mar 2006 at 18:25

I'm glad to see the fly makes it out intact in most scenarios at 80mph but why is my shopping such a mess in the boot when I get home when I don't even go over 30.

benjo plz. · 9 Mar 2006 at 18:27

Cause it was a mess before you started to go home

.

Oracle · 9 Mar 2006 at 18:32

This question was also posted at the back end of last year before I joined and it got flamed down then as rubbish! The fly does not have to fly at 80 to keep up with the car as the fly is not trying to cut through air! Open the window, let the fly out....see what happens to it!

singist · 9 Mar 2006 at 18:52

so......

A fly with a lit torch inside a plane taxiing at the speed of light on a treadmill is watching a clock in the jungle; what time does the tree fall?

Inquisitor · 9 Mar 2006 at 18:59

singist said:
so......

A fly with a lit torch inside a plane taxiing at the speed of light on a treadmill is watching a clock in the jungle; what time does the tree fall?

How can a plane taxi at the speed of light while at the same time being stationary on a treadmill?

Melm0 · 9 Mar 2006 at 19:01

*Squishes the fly*

End of discussion.