Fly in a car problem

Originally posted by uzless
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. 😉

It takes a net force on a body to change the velocity of that body.

The only forces acting on the fly are gravity and the upward thrust created by its wings. These forces are equal and opposite (thus, the fly is "hovering"😉, so there is no net force on the fly.

So to answer your question (as the above posters already have), yes, the fly is in the same position with respect to the car, assuming that the car maintains a constant velocity.

ok i'll say it again flies can't hover.

Originally posted by uzless
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. 😉


well, does you're christmas tree air freshener stick to the roof of the car when you're on the motorway doing 100kph? It remains vertical because the car is, believe it or not pressurized.

Get on the motorway and get up a decent speed, then open a window and you're ears will pop as if you're in a light aircraft.

but you already know that cos u posted the question.

ok.

Originally posted by richjohnson
It takes a net force on a body to change the velocity of that body.

The only forces acting on the fly are gravity and the upward thrust created by its wings. These forces are equal and opposite (thus, the fly is "hovering"😉, so there is no net force on the fly.

So to answer your question (as the above posters already have), yes, the fly is in the same position with respect to the car, assuming that the car maintains a constant velocity.

Okay, this one is tough to explain but here goes as I see it.

Gravity is pulling the fly down the vertical axis. To counter this force, the fly hovers straight up vertically. The problem is that the car is moving at 100 km/h horizontally. Once the fly jumps off the seat, it is no longer being pushed by the car horizontally.

Gravity is slowing the fly down on BOTH the horizontal and vertical axis. The fly is only counter-acting the vertical axis. It will slowly slow down and eventually get smacked by the glass window at the back of the car unless it flys forward.

The fly would slowly slow down and would have to slowly increase its forward velocity in order to keep up with the car, eventually reaching 100km/h. Similiar to a Harrier fighter jet take off.

I think this is why you always see flys at the back of your car and not the front 😉

Originally posted by uzless
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. 😉

To get the true motion of the fly you would have to account for the fact the earth at its surface is moving about 1600 Km/hr, going around the sun at 20+Km/sec, the solar system is moving towards a certain point in the sky at about 200 Km/sec so adding all that up, the fly should be dizzy by now!
If you discount all that, the frame of referance of the fly is moving so the fly does not have to expend energy to move 100Km/hr, just enough energy to hoover. It is still moving at 100KM/hr to an outside observer but zero to an observer inside the car.

Originally posted by sonhouse
To get the true motion of the fly you would have to account for the fact the earth at its surface is moving about 1600 Km/hr, going around the sun at 20+Km/sec, the solar system is moving towards a certain point in the sky at about 200 Km/sec so adding all that up, the fly should be dizzy by now!
If you discount all that, the frame of referance of the fly ...[text shortened]... r. It is still moving at 100KM/hr to an outside observer but zero to an observer inside the car.

Lol!

well, it can remain hoverin if the windows r shut!!!


whereas, if the windows r open, it'll have to perform the feat of flyin at a 100 kmph!!!

Originally posted by srikantan
well, it can remain hoverin if the windows r shut!!!


whereas, if the windows r open, it'll have to perform the feat of flyin at a 100 kmph!!!

If I'm in a moving bus and I jump straight up and down, eventually I will end up at the back of the bus because the bus is moving underneath me. Same with the fly.

Originally posted by uzless
If I'm in a moving bus and I jump straight up and down, eventually I will end up at the back of the bus because the bus is moving underneath me. Same with the fly.

obviously you've never been on a bus, or taken a physics course in your life.

Originally posted by aginis
obviously you've never been on a bus, or taken a physics course in your life.

http://www.newton.dep.anl.gov/askasci/phy00/phy00855.htm


Looks like inertia wins and the fly can stay there all he wants.

Originally posted by uzless
If I'm in a moving bus and I jump straight up and down, eventually I will end up at the back of the bus because the bus is moving underneath me. Same with the fly.

If you were on a bus travelling at 100 km/h, if you jumped up and down and there were no resistive forces upon your body in the vector in which you were travelling, then you would continue to travel at 100km/h. This assuming that gravity was acting upon the bus and you at right angles to the direction you were travelling in, ie you were on the flat.