Science Something amazing to tell you concerning physics and motion - Page 25

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.

headsnap · 06-04-2009, 08:18 PM

Quote:

Originally Posted by orange

They are not because they can't. They propel the treadmill. The energy from the engines' thrust moves the wheels and the treadmill equally.

for clarification, could you please post a picture of a JET that is entirely propelled by it's wheels?

orange · 06-04-2009, 08:18 PM

Quote:

Originally Posted by cdcox

So if you put a sail on a roller skate and sit it on a treadmill there is no wind powerful enough to propel the roller skate forward?

Not if the treadmill spins as freely as the skates. You get the gears analogy, right? You seem to be coming around.

orange · 06-04-2009, 08:19 PM

Quote:

Originally Posted by headsnap

for clarification, could you please post a picture of a JET that is entirely propelled by it's wheels?

Answer my question. Then I'll respond to you.

Your comment earlier just proves you have no answer.

Nighty-night.

headsnap · 06-04-2009, 08:19 PM

Quote:

Originally Posted by cdcox

So if you put a sail on a roller skate and sit it on a treadmill there is no wind powerful enough to propel the roller skate forward?

dun,not when the wind is also propelling the treadmill in the opposite direction...

headsnap · 06-04-2009, 08:21 PM

Quote:

Originally Posted by orange

Answer my question. Then I'll respond to you.

Your comment earlier just proves you have no answer.

Nighty-night.

your question is a plane crash... it's doesn't fly but it is most definitely moving forward.

One again, IS THIS PLANE ENTIRELY PROPELLED BY IT'S WHEELS?

headsnap · 06-04-2009, 08:22 PM

Quote:

Originally Posted by orange

Not if the treadmill spins as freely as the skates. You get the gears analogy, right? You seem to be coming around.

What force is counteracting the wind?

remember Newton...

prhom · 06-04-2009, 08:25 PM

Here's a cool experiment that's a pretty fun statics problem to prove. Take a yard stick or any stick like a dowel, spread out your hands and balance it on your index fingers. Then slide your hands toward each other. You will notice that the weight transfers between the two fingers until they come together. That point is the center of mass for that object.

**cdcox** · 06-04-2009, 08:26 PM

Quote:

Originally Posted by orange

They are not because they can't. They propel the treadmill. The energy from the engines' thrust moves the wheels and the treadmill equally.

Not this.

This.

orange · 06-04-2009, 08:31 PM

If that bar is free to move, it will move, the gear will spin and whatever is attached to that axle will stay where it is.

**cdcox** · 06-04-2009, 08:35 PM

Quote:

Originally Posted by orange

If that bar is free to move, it will move, the gear will spin and whatever is attached to that axle will stay where it is.

Both the bar and the gear are free to move relative to the ground. Their relative velocities will depend on the net force balances on the two objects.

headsnap · 06-04-2009, 08:35 PM

Quote:

Originally Posted by orange

If that bar is free to move, it will move, the gear will spin and whatever is attached to that axle will stay where it is.

not if I push it...

orange · 06-04-2009, 08:38 PM

Quote:

Originally Posted by cdcox

Both the bar and the gear are free to move relative to the ground. Their relative velocities will depend on the net force balances on the two objects.

I've pointed out that my treadmill must have equal or less resistance to spinning (i.e. moving forward in its own direction) than the plane has to going forward.

Keep in mind the gear IS moving. When it spins, it's moving. No forward movement by axle etal is necessary to satisfy that.

headsnap · 06-04-2009, 08:48 PM

Quote:

Originally Posted by headsnap

One again, IS THIS PLANE ENTIRELY PROPELLED BY IT'S WHEELS?

WELL?

**cdcox** · 06-04-2009, 08:52 PM

Quote:

Originally Posted by orange

I've pointed out that my treadmill must have equal or less resistance to spinning (i.e. moving forward in its own direction) than the plane has to going forward.

Okay.

prhom · 06-04-2009, 08:56 PM

Wow, I'm amazed that you guys are still arguing the plane on the treadmill. This is a classic physics test question that takes something that seems to complicate the problem (the treadmill) but is really just a distraction. Planes only fly based on AIRSPEED. Anything related to the groundspeed is irrelevant as to whether the plane will fly or not!! Besides, there would only be an extremely neglible force imparted to the treadmill by the plane's wheels. This would be from friction generated in the wheel bearings and rolling resistance in the tires. Bottom line the plane is going to fly no matter how fast or slow the treadmill is going.

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, 08:25 PM	#367
prhom Veteran Join Date: Nov 2007 Location: Denver Casino cash: $7406013	Here's a cool experiment that's a pretty fun statics problem to prove. Take a yard stick or any stick like a dowel, spread out your hands and balance it on your index fingers. Then slide your hands toward each other. You will notice that the weight transfers between the two fingers until they come together. That point is the center of mass for that object.
Posts: 2,267

06-04-2009, 08:31 PM	#369
orange MVP Join Date: Sep 2000 Location: Denver, CO Casino cash: $10004900	If that bar is free to move, it will move, the gear will spin and whatever is attached to that axle will stay where it is.
Posts: 11,661

06-04-2009, 08:56 PM	#375
prhom Veteran Join Date: Nov 2007 Location: Denver Casino cash: $7406013	Wow, I'm amazed that you guys are still arguing the plane on the treadmill. This is a classic physics test question that takes something that seems to complicate the problem (the treadmill) but is really just a distraction. Planes only fly based on AIRSPEED. Anything related to the groundspeed is irrelevant as to whether the plane will fly or not!! Besides, there would only be an extremely neglible force imparted to the treadmill by the plane's wheels. This would be from friction generated in the wheel bearings and rolling resistance in the tires. Bottom line the plane is going to fly no matter how fast or slow the treadmill is going.
Posts: 2,267