Down wind faster than the wind

[spork]

Wow.

All that just to gloss over the fact that JB won't admit that he missed the context of the original question.

Very telling....

[Seymour's brain]
Hmmm.... I've made a bunch of statements that prove to be completely false. How embarrassing. But wait - let's cast this in another light. Maybe the guy that pointed it out simply didn't understand the context in which I made those wrong statements. Yeah - that's it. Sounds much better. Phew! That was close.[/Seymour's brain]

 

[jsfisher]

What is it with you guys and your fixation with relative velocities?

You were the one that said the collisions were different depending on which one was moving. In fact, you said:

If a 1kg mass hits a stationary 10kg mass, the total momentum is much less than a 10kg mass hitting a stationary 1kg mass. (Same velocities)
Free space or not.
From the point of view of each of the masses, in each collision, their relative velocities remain equal from each viewpoint, but the actual events are different. They are not equivalent.

(My bolding.) So, if they are not equivalent, how do you tell them apart?

 

[ThinAirDesigns]

Without a comparable cart without gears to the wheel, it is difficult to say which would be the faster.

It's not difficult at all.

A: The cart without the prop geared to the wheels will never reach the speed of the wind.

B: The cart with the prop geared to the wheels goes DDWFTTW repeatedly and on demand.

JB

 

[Seymour Butz]

Now the "thrust" component of the propeller's output can push the cart to the right. But if the wheels are not providing power, where does the thrust come from? The prop will continue to turn from momentum ( as seen on the video) and that is more than enough.

The cart moves up, friction is regained and lost momentum restored, until the next time. There is no "next time", because the process is essentially continuous.

This is the transition that I'm having a problem with.

The rest I agree with too.

 

[Seymour Butz]

[Seymour's brain]
Hmmm.... I've made a bunch of statements that prove to be completely false. How embarrassing. But wait - let's cast this in another light. Maybe the guy that pointed it out simply didn't understand the context in which I made those wrong statements. Yeah - that's it. Sounds much better. Phew! That was close.[/Seymour's brain]

[JB's brain]
Man, I totally missed the context of the original question, and got called out on it. But damn, I'm here trying to convince everyone that the cart works, so I can't have it look like I'm a fool. That'll just lessen my credibility, and I can't have that when I'm trying to make claims that I have no clear evidence for. Maybe if I ignore Seymour's question about whether or not I understood the original question and construct strawmen that I can say I easily refuted, and get my other delusional friends to back me here, maybe I can make my case for the cart actually working without actually having to produce that clear evidence. Then my delusional beliefs can continue undiminished. Phew! That was close. [JB's brain]

 

[humber]

You need to actually do the math before you can get an answer. To make the problem easier, assume that the astronaut sticks to the space craft when they smush together. That way, you only have to worry about conservation of momentum to solve for motion of the collision result.

You are an observer outside of the spacecraft and to your perspective the spacecraft is not moving. You see the astronaut approaching from your right and crashes directly into the spacecraft. You even were fortunate enough to get the encounter on tape. Now, what difference will you see to prove that spacecraft was at fault for running into the astronaut and not the other way around. The court is going to want to see your calculations for what would be expected to show up on the tape in each case.

Fantastic. Answer this. What is the difference between two billiard balls colliding at 10m/s and two tankers doing the same? Big release of energy in one case, other not so much.
Velocities are no indicator, because they are collisions that differ in magnitude. That makes them not the same. I call those "not the same"
Similarity 10kg moving mass, 1kg static mass. Different level of collision when transposed.
"The observer cannot tell the difference"- My Little Book of Relativity

 

[humber]

It's not difficult at all.

A: The cart without the prop geared to the wheels will never reach the speed of the wind.

B: The cart with the prop geared to the wheels goes DDWFTTW repeatedly and on demand.

JB

That is the evidence that is missing , JB.
It would not be easy to demonstrate, because the average velocity of the wind cannot be determined over a short distance. It would need, I think, a long run.
The cart could be put against a strain gauge, with a blower as a source.
The two could be tested to determine which could generate the greater force.
As far as the string on treadmill goes, if the thread is fine so that it does not become a drag or load, then I would expect no difference.

 

[humber]

This is the transition that I'm having a problem with.

The rest I agree with too.

Aahh, at least one.
I think that the vibration the belt motor could contribute a stimulus.
There is enough energy in the prop to cover a small step. It would only require a momentary increase in the friction of the wheels to regain the lost energy, and the process would cycle.

 

[ynot]

Ynot, I spoke with spork on the phone about that test this evening. We both agreed it's a fine test to do and will be done. I'll try to drop by his house before work in the morning and get it done.

I'm interested in what you think the difference might be in using the string to get up to speed, or my hand?

JB

The only test I‘ve seen of this type has been at the front of the tread when the cart has a lot of stored energy (in my opinion). Also the hand wasn‘t very steady and consistent as a stop. The rate that the propeller loses energy when it remains on the moving tread is much more gradual and slow than when it is taken off the tread. Given the lightness of your cart and the energy involved it should be left for quite some time to allow all the stored energy can used. A stop at the back end of the tread would do the same thing as the string but the string would hold the cart in the center of the tread better.

I await the test results with interest.

 

[humber]

"Captain! Missile approaching starboard"

"Don't be hasty Jenkins, we could be moving towards it, and less of your "starboard"
fascism."

Here's a clue. The prior history of the object is important. I know, it's not in the formula.

 

[Michael C]

Fantastic. Answer this. What is the difference between two billiard balls colliding at 10m/s and two tankers doing the same? Big release of energy in one case, other not so much.
Velocities are no indicator, because they are collisions that differ in magnitude. That makes them not the same. I call those "not the same"
Similarity 10kg moving mass, 1kg static mass. Different level of collision when transposed.
"The observer cannot tell the difference"- My Little Book of Relativity

Velocity is a relative property, mass is not.

 

[Michael C]

Sleight of hand. The average velocity of the hand, must equal the average velocity of the cart. If the operator does not apply force with 100% duty cycle,but in short bursts, that will lead to the given effect.

No. The hand moves slower than the cart. Why not make one and try it out?

 

[humber]

Velocity is a relative property, mass is not.

There are no "relative properties" objects have properties. There are fundamental properties, such as mass and charge. Displacement and velocity are not fundamental properties.

 

[Dan O.]

Problem A: 10kg mass moving at 1m/s strikes a 1kg stationary mass. If the collision is inelastic, the combined 11kg mass (calculated using conservation of momentum) continues moving at (10*1+1*0)/11 = about .91m/s. For the observer that was also moving at 1m/s, the collision mass is now moving at a relative velosity of 1-.91 = 0.09m/s. The initial kinetic energy (1/2 mv²) was 5 joules and the final ke is about 4.55 joules. The missing .45 joules was converted to heat.

Problem B: A 10kg stationary mass is struck by a 1kg mass moving at 1m/s. Agian, for and inelastic collision, the combined mass moves at (10*0+1*1)/11 = about 0.09m/s relative to the observer that was not moving. The kinetic energy was initially 10*0*0/2+1*1*1/2=0.5 and after the collision is 11*(0.09)²=0.05 joules again leaving 0.45 joules converted to heat.

To the observer, both collisions looked exactly the same. If you want, you can try the calculations for an elastic collision. In this case, the kinetic energy is conserved instead of being converted into heat.

 

[ThinAirDesigns]

The only test I‘ve seen of this type has been at the front of the tread when the cart has a lot of stored energy (in my opinion).

When you say "of this type", I don't get it ... we've never started the device with a string before.

Also the hand wasn‘t very steady and consistent as a stop.

And now I'm completely confused. I thought you wanted us to *start* the machine using a string rather than the hand. Now your complaining about using a hand as a "stop". Starting the device with a string won't change the fact that something is going to have to "stop" the device when it get's to the top of the treadmill

I'm happy to do a test for you, but I'm not going to go out of my way until we both understand what you are actually want the test to be. Is this a "start" test, or a "stop test?

Given the lightness of your cart and the energy involved it should be left for quite some time to allow all the stored energy can used.

We already have videos posted where we show it rolling untouched for close to 2 minutes. I've asked you before and not received and answer - how freakin' long do you need to see it running before you figure out that it's not running on stored energy?

I await the test results with interest.

And you're going to keep awaiting them until I figure out what you wish to test. I'm not doing it ynot until you can tell me *exactly* how you want it set up, start to finish. This test is being done *only for you*, and performing a test that you then say "that wasn't what I wanted" is just a waste of time.

So, spell it out in its entirety and we'll chat about setting it up.

JB

 

[humber]

No. The hand moves slower than the cart. Why not make one and try it out?

I don't need to, Micheal C. The average velocity of the hand must be that of the cart, or it would accelerate away and leave the hand.
It is possible to move the device, while simultaneously pushing the hand back and forth, in oscillation, so that the journey of the hand will have a longer displacement, but the average would still be that of the cart.

He is playing a trick, by operating his hand in a similar way as the cart extends itself, but the movements are small, so you don't notice.
The integral of the applied force, will be that required to accelerate a simple skateboard, of the same mass and frictional load, to the same velocity.

 

[Michael C]

There are no "relative properties" objects have properties. There are fundamental properties, such as mass and charge. Displacement and velocity are not fundamental properties.

OK, at least you agree that mass and velocity are different animals.

If two billiard balls collide at 10 m/s and two tankers collide at 10 m/s, there is a big difference: the mass involved is different.

 

[Michael C]

No. The hand moves slower than the cart. Why not make one and try it out?

I don't need to, Micheal C.

You're clamouring to Spork about giving evidence, but you won't even try a simple experiment yourself to test your theories?

 

[ThinAirDesigns]

humber:

He is playing a trick, by operating his hand in a similar way as the cart extends itself, but the movements are small, so you don't notice.

I am a all powerful. The cart bends to my will. I ROCK!!!!

JB

 

[GreyICE]

If a 1kg mass hits a stationary 10kg mass, the total momentum is much less than a 10kg mass hitting a stationary 1kg mass. (Same velocities)
Free space or not.
From the point of view of each of the masses, in each collision, their relative velocities remain equal from each viewpoint, but the actual events are different. They are not equivalent.

Yes they are. Velocity is meaningless except as defined as a change in velocity. The energy term is ACCELERATION not velocity. Velocities may differ in reference frames with no energy loss, all measurements in all frames will give you the same laws.