Science Something amazing to tell you concerning physics and motion - Page 28

Jenson71 · 06-04-2009, 10:15 AM

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.

orange · 06-04-2009, 09:58 PM

Whatever horizontal energy the wheels are exerting is equally rolling the wheels and the treadmill. When the wheels have rolled forward one revolution, say, 10 feet, the treadmill will have moved ten feet under it. The plane will now be in contact with tread that WAS 10 feet in front of it - but is NOW directly underneath. The wheels have moved 10 feet. The treadmill has moved -10 feet. The plane hasn't moved.

Imagine a wheel spinning in mud. Lots of mud is flying out behind the wheel but the car ain't going anywhere.

Now let's make the car a rocket dragster. No power to the wheels. Does it somehow find traction and move? I still see lots of mud flying out the behind the wheel and a stuck car.

**cdcox** · 06-04-2009, 10:08 PM

Orange --

I'd seriously encourage you to do some simple experiments using ordinary household items to test your theories. Apply a force to a wheeled object such that it remains stationary while a free moving object below moves in the opposite direction as a result of the applied force to the upper object.

prhom · 06-04-2009, 10:11 PM

Quote:

Originally Posted by orange

Whatever horizontal energy the wheels are exerting is equally rolling the wheels and the treadmill. When the wheels have rolled forward one revolution, say, 10 feet, the treadmill will have moved ten feet under it. The plane will now be in contact with tread that WAS 10 feet in front of it - but is NOW directly underneath. The wheels have moved 10 feet. The treadmill has moved -10 feet. The plane hasn't moved.

This is where you're wrong though, the force required to spin the the wheels at a 1:1 ratio with the treadmill is less that the force that the plane can generate. It will continue applying force till the wheel's rotation is at a >1:1 ratio to the treadmill when the plane will gain speed and take off. I think the original question posed said that the treadmill was going at a constant speed. This is key, if the treadmill can accelerate then no, the plane will not take off. But it is erroneous to say that the treadmill will be pushed equally by the plane.

Hammock Parties · 06-04-2009, 10:13 PM

This is one nerdy-ass thread.

orange · 06-04-2009, 10:14 PM

Quote:

Originally Posted by prhom

This is where you're wrong though, the force required to spin the the wheels at a 1:1 ratio with the treadmill is less that the force that the plane can generate. It will continue applying force till the wheel's rotation is at a >1:1 ratio to the treadmill when the plane will gain speed and take off. I think the original question posed said that the treadmill was going at a constant speed. This is key, if the treadmill can accelerate then no, the plane will not take off. But it is erroneous to say that the treadmill will be pushed equally by the plane.

Why? The treadmill can spin at any speed the wheels can. The wheels' rotation will never be > the treadmill's.

Tell me what assumptions you're making to conclude the treadmill can't match the wheels' speed. In the original problem (mine is a variant), in fact, the treadmill matching the wheels' speed is an explicit condition.

orange · 06-04-2009, 10:16 PM

Quote:

Originally Posted by cdcox

Orange --

I'd seriously encourage you to do some simple experiments using ordinary household items to test your theories. Apply a force to a wheeled object such that it remains stationary while a free moving object below moves in the opposite direction as a result of the applied force to the upper object.

I've already provided my simple experiments - car on rollers at an emissions test, car in mud. Neither move. You guys are arguing that somehow being a plane makes it different. I'm saying no, not until you have some airspeed and lift - which you will never get with a groundspeed of 0.

**cdcox** · 06-04-2009, 10:17 PM

Quote:

Originally Posted by orange

Why? The treadmill can spin at any speed the wheels can.

Not if the motive force is applied to the plane.

Try it at home with reasonable sized objects and see.

Silock · 06-04-2009, 10:17 PM

Quote:

Originally Posted by orange

I've already provided my simple experiments - car on rollers at an emissions test, car in mud. Neither move. You guys are arguing that somehow being a plane makes it different. I'm saying no, not until you have some airspeed and lift - which you will never get with a groundspeed of 0.

So, video proof means nothing to you, does it?

prhom · 06-04-2009, 10:18 PM

Quote:

Originally Posted by orange

I've already provided my simple experiments - car on rollers at an emissions test, car in mud. Neither move. You guys are arguing that somehow being a plane makes it different. I'm saying no, not until you have some airspeed and lift - which you will never get with a groundspeed of 0.

Wheels move these vehicles via a transmission. That has been key to this whole argument, a plane's wheels are not geared. The bearings for all intents and purposes are frictionless.

**cdcox** · 06-04-2009, 10:22 PM

Quote:

Originally Posted by orange

I've already provided my simple experiments - car on rollers at an emissions test, car in mud. Neither move. You guys are arguing that somehow being a plane makes it different. I'm saying no, not until you have some airspeed and lift - which you will never get with a groundspeed of 0.

In both of your examples the motive force is applied to the wheels. I agree in this case. I've wedged cardboard under the front of my drive wheels and shot it out the back when my wheels have been on ice. But if a tow truck were pulling my car, over cardboard on ice, no way would it shoot the cardboard out the back wheels. Likewise if I had a rear-wheel-drive car and put the cardboard under the front wheels.

It matters where the force is!

orange · 06-04-2009, 10:23 PM

Quote:

Originally Posted by Silock

So, video proof means nothing to you, does it?

Video "proof" requires actually not rigging the experiment to fail.

I'm not sure which video you're referring to but that Mythbusters thing is crap.

prhom · 06-04-2009, 10:24 PM

Well shit, I reread the original dumba$$ post from magic hef and I thought it said that the conveyor went a constant speed. It does not, it say "match the speed of the wheels", my bad orange. I should have re-read that question. As long as the conveyor has the ability to accelerate to match the wheels rotation then the plane won't take off. Sorry for all that trouble. Why didn't you just tell me to re-read the question?? I've just wasted an hour of my life. Dammit.

orange · 06-04-2009, 10:25 PM

Quote:

Originally Posted by prhom

Wheels move these vehicles via a transmission. That has been key to this whole argument, a plane's wheels are not geared. The bearings for all intents and purposes are frictionless.

Of course that's wrong and impossible BUT my treadmill is every bit as frictionless as your bearings.

orange · 06-04-2009, 10:27 PM

Quote:

Originally Posted by cdcox

In both of your examples the motive force is applied to the wheels. I agree in this case. I've wedged cardboard under the front of my drive wheels and shot it out the back when my wheels have been on ice. But if a tow truck were pulling my car, over cardboard on ice, no way would it shoot the cardboard out the back wheels. Likewise if I had a rear-wheel-drive car and put the cardboard under the front wheels.

It matters where the force is!

Not in the rocket car in the mud - and you can extend it to a rocket car on the emissions rollers. All of the motive force on the plane/car MUST be transfered to the wheels or the plane/car will tip over.

That tow truck has a purchase. The jet's only purchase - wherever the jet engines are - is the wheels on the moving treadmill.

**cdcox** · 06-04-2009, 10:29 PM

Quote:

Originally Posted by prhom

Well shit, I reread the original dumba$$ post from magic hef and I thought it said that the conveyor went a constant speed. It does not, it say "match the speed of the wheels", my bad orange. I should have re-read that question. As long as the conveyor has the ability to accelerate to match the wheels rotation then the plane won't take off. Sorry for all that trouble. Why didn't you just tell me to re-read the question?? I've just wasted an hour of my life. Dammit.

Read the whole thread.

06-04-2009, 10:15 AM
Jenson71 fides quaerens intellectum Join Date: Oct 2003 Location: United States Casino cash: $8330900	Something amazing to tell you concerning physics and motion 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.
Posts: 15,986

06-04-2009, 09:58 PM	#406
orange MVP Join Date: Sep 2000 Location: Denver, CO Casino cash: $10004900	Whatever horizontal energy the wheels are exerting is equally rolling the wheels and the treadmill. When the wheels have rolled forward one revolution, say, 10 feet, the treadmill will have moved ten feet under it. The plane will now be in contact with tread that WAS 10 feet in front of it - but is NOW directly underneath. The wheels have moved 10 feet. The treadmill has moved -10 feet. The plane hasn't moved. Imagine a wheel spinning in mud. Lots of mud is flying out behind the wheel but the car ain't going anywhere. Now let's make the car a rocket dragster. No power to the wheels. Does it somehow find traction and move? I still see lots of mud flying out the behind the wheel and a stuck car. Last edited by orange; 06-04-2009 at 10:11 PM..
Posts: 11,661

06-04-2009, 10:08 PM	#407
cdcox www.nfl-forecast.com Join Date: Sep 2000 Casino cash: $-478231	Orange -- I'd seriously encourage you to do some simple experiments using ordinary household items to test your theories. Apply a force to a wheeled object such that it remains stationary while a free moving object below moves in the opposite direction as a result of the applied force to the upper object.
Posts: 46,032

06-04-2009, 10:13 PM	#409
Hammock Parties I'll be back. Join Date: Nov 2002 Casino cash: $980478	This is one nerdy-ass thread. __________________ Chiefs game films
Posts: 296,836

06-04-2009, 10:24 PM	#417
prhom Veteran Join Date: Nov 2007 Location: Denver Casino cash: $7406013	Well shit, I reread the original dumba$$ post from magic hef and I thought it said that the conveyor went a constant speed. It does not, it say "match the speed of the wheels", my bad orange. I should have re-read that question. As long as the conveyor has the ability to accelerate to match the wheels rotation then the plane won't take off. Sorry for all that trouble. Why didn't you just tell me to re-read the question?? I've just wasted an hour of my life. Dammit.
Posts: 2,267