Something amazing to tell you concerning physics and motion

[Jenson71]

This blows my mind.

Okay, say you have two ball bearings. You hold one in your hand and drop it. The other you put in a gun, point it straight forward, as level as the one in your hand, and pull the trigger, sending it hundreds of yards.

Which one lands first?

The one dropped in your hand right? RIGHT!?!?

No, actually they both hit the ground at the same time.

This is because the vertical component of motion is the same for both objects. They both fall vertically the same distance at about 10 meters per second squared (gravity, actually more like 9.8).

But Jenson, Jenson! What about the horizontal component of the gun-fired ball bearing? Actually, when air resistance is small enough to ignore as it is in this case (being that the bearings are exactly alike), the horizontal and vertical components of a projectile's velocity are completely independent of one another.

And, in this experiment, the gun-fired bearing is constantly falling from the moment it is fired. Yes, it looks like it is holding up in a straight line, but, it's actually falling and it's just hard to see with our eyes. And again, it is falling at exactly the same speed as the ball bearing you released in your hand -- the speed of gravity.

Post more cool science things in this thread.

I think I will later post Aristotle vs. Galileo and gravity, for a little history spin on science.

[prhom]

Originally Posted by cdcox

The problem statement (at least some versions of it) say the treadmill moves at the same rate as the wheels of the plane.

This statement causes a violation of Newton's second law.

It doesn't really violate it so much as complicate it by making it a dynamics problem where you have to account for rotational acceleration and momentum. Not a simple force balance.

[Silock]

Originally Posted by orange

Send me the money. All I need is the video recorder and the rocket engine - I can (generously) supply the rest.

Alternatively, you can try emailing my experiment to the Mythbusters guys, but will they ever read it? I think I have a better chance of getting a video recorder from you.

I WILL keep an eye out for something already online, though. Perhaps I can come up with a smarter search string than I've been using.

Hot Wheels car + model rocket engine + treadmill

[Joe Seahawk]

Originally Posted by prhom

The plane wheels can never go faster than the treadmill because the original question said that the treadmill is designed to ALWAYS go as fast as the plane's wheels. Because of that statement we have to assume that as the plane accelerates and starts to gain on the treadmill, some control makes the treadmill accelerate and convert the plane's incremental thrust into ROTATIONAL acceleration and momentum in the wheels. By the way the problem is defined, the plane can never convert thrust into a higher incremental wheel speed versus the treadmill. THis has no basis in reality, and therefore cannot be proved by a simple experiment.
(At least it would require very complicated machinery to balance a model plane's thrust and treadmill acceleration)

Apparently I misunderstood the question.. I thought the treadmill moved one direction in the same speed as the PLANE thrust propelled it in the opposite direction.

[prhom]

Originally Posted by Joe Seahawk

Apparently I misunderstood the question.. I thought the treadmill moved one direction in the same speed as the PLANE thrust propelled it in the opposite direction.

Yep, so did I for about an hour just look at the post history. I now feel compelled to make sure people catch that very important part of the question. The treadmill can adjust it's speed infinitely. THat changes everything.

[Silock]

If the plane isn't moving forward, why is the treadmill moving?

It DOESN'T MATTER if the treadmill can adjust its speed. If the plane isn't going forward, the treadmill won't be moving.

[orange]

Originally Posted by orange

Send me the money. All I need is the video recorder and the rocket engine - I can (generously) supply the rest.

Originally Posted by Silock

Hot Wheels car + model rocket engine + treadmill

Good thinking. Scratch the rocket engine. Now then, as for the other part...

[orange]

Originally Posted by Silock

If the plane isn't moving forward, why is the treadmill moving?

It DOESN'T MATTER if the treadmill can adjust its speed. If the plane isn't going forward, the treadmill won't be moving.

The plane tries to go forward. The energy for this motion is emparted to the wheels which try to roll. Unfortunately the ground (treadmill) rolls under them at equal and opposite speed so the plane goes nowhere.

[Joe Seahawk]

Originally Posted by prhom

Yep, so did I for about an hour just look at the post history. I now feel compelled to make sure people catch that very important part of the question. The treadmill can adjust it's speed infinitely. THat changes everything.

Well, than now it makes my head hurt.. I'm going to the epic fail thread!

[cdcox]

Originally Posted by prhom

It doesn't really violate it so much as complicate it by making it a dynamics problem where you have to account for rotational acceleration and momentum. Not a simple force balance.

This is the first idea that proposes at least a reasonable way to make it all hold together. I only wonder if the force needed to accelerate the wheels isn't coming from the treadmill motor rather than the jet engine? Unclear.

I'd calling it a night, and will do my best not to click on this thread at work tomorrow.

[Silock]

Originally Posted by orange

The plane tries to go forward. The energy for this motion is emparted to the wheels which try to roll. Unfortunately the ground (treadmill) rolls under them at equal and opposite speed so the plane goes nowhere.

That is not possible.

[Joe Seahawk]

Originally Posted by Silock

That is not possible.

I'm with you silock.. I dont thing the jet engines give a **** what the wheels are doing, as long as they roll freely, and are not seized.

[jackkked]

> THE RIDDLE
> There are 7 girls in a bus.
> Each girl has 7 backpacks.
> In each backpack, there are 7 big cats.
> For every big cat there are 7 little cats.
>
> Question: How many legs are there in the bus?
>

[orange]

[bdeg]

Originally Posted by jackkked

> THE RIDDLE
> There are 7 girls in a bus.
> Each girl has 7 backpacks.
> In each backpack, there are 7 big cats.
> For every big cat there are 7 little cats.
>
> Question: How many legs are there in the bus?
>

how many boys are there on the bus?

[bdeg]

if 0
2(busdriver)+7x7x7x7x4+7x7x7x4+7x2
2+9604+1372+14
10992
if busdriver is a female with a backpack then

10990