a fly can stop a train?

Originally posted by chasparos
I'll throw something in here.
Firstly assume this:
We as the observers defines movement. Relative motion
does only complicate things.

Lets agree that velocity is change in position per time unit.
This means that if you look at the scene frosen in a single
instant no movement ever occurs. A velocity of zero can therefore be sustanied either inde ...[text shortened]... measure a change in position. Thus, speed.
The fly never stops. And the train doesnt either :-)

actualy, a very small section of the windshield _would_ have to have 0 vilosity for a point of time. this is aceptable because the windsheild flexes.

What was the last thing that entered the fly's mind when it hit the train?


It Arse.

Why doesn't someone just take a stopwatch and a fly down to the railway track and find out?

*cough*
http://www.physlink.com/Education/AskExperts/ae281.cfm
*cough*

😉

Max Planck would have something to say about this.

Originally posted by ark13
No, that's incorrect. Since the fly's velocity is changing 180 degrees, there's a time in which the fly is completely stationary. It's a very short time, but we know it's there, because of the knowledge that accelerations don't happen instantaniously.

Another similar question is if a piston in a combustion engine ever stops as the engine runs? Remember, it is directly connected to a crank moving in an endless circle!

So motion is some kinda paradox, or whatever.
If you what to be technical about is nothing EVER stops, even if you sit on your ass like a stone, you are falling (orbiting) toward the sun.
scale the logic either way.

The train cannot be stationary as where does it obtain the momentum form instantly following the collision with the fly. This implies that the train may overcome inertia and accelerate to the same speed in an instant.