Helicopter on a turntable

[wbradley]

I never heard the actual riddle completely. I wasnt told the prop speed had to be equal to the treadmill speed until after .

[JDMenrique]

I'm going to say no and here's why. Helicopters and airplanes are completely different, even though the concept of air passing over a rotor blade and a fixed wing are relatively similar you must take torque into account.

By the time the turntable spins fast enough to create any kind of lift, the toy helicopter would have spun out of control. Think of it as a toy top after it is spun, torque will take the object in the direction it is spinning. This concept also applies when shooting at long distances, the rotation of the projectile will cause spindrift.

A helicopter counter acts torque with a tail rotor. Being that this toy is not functional I would see it rotating fast enough to just topple over.

[frosty86]

This reminds me of troll science

[b.e]

A ship full of iron ore pulls into a lock, which is then closed. The water level is measured. Then the cargo is dumped over the side into the water.

What happens to the water level in the lock?

[neutron256]

Originally Posted by b.e

A ship full of iron ore pulls into a lock, which is then closed. The water level is measured. Then the cargo is dumped over the side into the water.

What happens to the water level in the lock?

Water level will go down some.

The ship will always displace a volume of water equivalent to its weight.

When in the ship the iron ore will displace a volume of water equivalent to its weight, but in the water iron ore would sink only displacing a volume of water exactly the same as the volume of the ore itself.

[celica73]

What if the cargo ship was full of witches?

[MmmHamSandwich]

Originally Posted by celica73

What if the cargo ship was full of witches?

Build a bridge out a em?

[snapspinner]

Build a bridge out a em?

I see you are learn'ed in the ways of science.

To answer the first riddle. In reality the helicopter rotates until it gets out of balance at which point it destroys itself in a tornado of swirling parts. Theoretically, if it where possible to build a perfect balanced helicopter that would actually stay centered on the turntable at rotor speeds the Helicopter would not fly.

The airplane on the treadmill riddle. In reality the plane always flys. If you don't understand I ain't going to explain it.

Now if you put a duck on treadmill would it quack or fly off?

[ichitaka05]

Originally Posted by snapspinner

Now if you put a duck on treadmill would it quack or fly off?

That's not a good example. Duck can generate enough wind velocity to fly by flapping its wings vs airplane cannot.

If treadmill can generate enough power & speed, it can push the airplane back due to airplane mass weight & wheel frictions.

Edit: also birds jumps first before they fly. If you can nueturized the jump force, bird cannot fly!

[ette]

"What... is the air-speed velocity of an unladen swallow?"

"What do you mean? An African or European swallow?"

[HunterGreene]

Originally Posted by ette

"What... is the air-speed velocity of an unladen swallow?"

"What do you mean? An African or European swallow?"

I don't know that! WAAAAAAAAAAAAAAAAAAAAAAAAAAAaaaaaaaaaaaaaaaaahhhhh ...

But seriously, folks.

Originally Posted by wbradley

Ahh, I was basing this on the theoretical, so the "treadmill" has no speed limit. And I am sure that if the net resistance from the axle and the resistance to acceleration due to mass of the spinning wheels equalled say 1% of the thrust, we woild need to travel at 10,000 mph for a 100 mph prop speed.

Nobody is wrong here, the experiment is well known. So are the theories of physics.

Please just admit that in theory I am correct. You are correct in practice however.

Anything is possible "in theory." In the theory of the Multiverse, in another universe, I am supreme dictator of the Solar system and planes don't fly on treadmills. In our universe however, using the everyday (macro) laws of physics (which thank God don't change), you will currently not be able to produce the treadmill necessary to counteract the force generated by the jet/prop. You may be able to say you are correct "in theory," but "In theory," 2+2=mastadon. Theories don't count here. Practice does.

Originally Posted by b.e

A ship full of iron ore pulls into a lock, which is then closed. The water level is measured. Then the cargo is dumped over the side into the water.

What happens to the water level in the lock?

The answer is no level change. Whoever posted earlier that the ship always displaces its weight is correct. However, if you remove the cargo from the ship, the ship is now filled with air instead of the much denser iron, which actually makes the ship more buoyant, so the ship rises, but the water level does not change. Living/sailing on the Great Lakes, I see this all the time in the freighters that are constantly going in and out of Cleveland's ports:



The numbers you see on the very front near the waterline are there to show how much cargo she is carrying. The more weight, the lower the boat sits in the water and as in this case, the less, the higher. The water level will not change if the ore is removed.

[wbradley]

When the ore is in the ship the ship sinks further in the water due to it's Sg (specific gravity/ or density) increasing relative to the water, reducing its buoyancy.

However when you dump the ore in the water you reduce the Sg of the ship causing it to rise and displace less water. And, the ore in the water has a higher Sg that exceeds that of the water causing it to become fully submerged.

Ore in ship-displaces X water as buoyance decreases.

Ore in water-displaces volume of ore Y plus reduced volume of ship hull X2.

Id say in the end it should be equal as the ship drops enough to displace equal to the ore volume when it is loaded.

[neutron256]

The answer is no level change. Whoever posted earlier that the ship always displaces its weight is correct. However, if you remove the cargo from the ship, the ship is now filled with air instead of the much denser iron, which actually makes the ship more buoyant, so the ship rises, but the water level does not change. Living/sailing on the Great Lakes, I see this all the time in the freighters that are constantly going in and out of Cleveland's ports:



The numbers you see on the very front near the waterline are there to show how much cargo she is carrying. The more weight, the lower the boat sits in the water and as in this case, the less, the higher. The water level will not change if the ore is removed.

The ship itself displaces a volume of water equal to its weight.

The iron ore in the ship also displaces a volume of water equal to its weight.

When the iron ore is in the water it sinks so it can never displace more water then its own volume.

The iron ore will displace some water but based on its volume rather then its weight like it did when it was in the ship.

This is why things sink or float.

Density < Water: the object will displace a volume of water equal to its weight and float.

Density > Water: the object will displace a volume of water equal to its own volume and sink

[7thgear]

not sure if helpful

[ame="http://www.youtube.com/watch?v=6a62ul8W0aQ"]helicopter turntable - YouTube[/ame]