Physics Quest

[Matos de Matos]

Hi everybody:

The bob will stop at which position?
1, 2, or 3 for A and B.
The explanation and some math will elucidate us, but the poll is open to all.
Thank you
David

[Sephiroth]

Guessed 1 for both, but I would have guessed 2 if you mentioned that the system was without losses

3 would be nice though

[Matos de Matos]

Guessed 1 for both, but I would have guessed 2 if you mentioned that the system was without losses

3 would be nice though

Sorry, it is a frictionless (magnetic bearing) fulcrum and perfect elastic collision.
The velocity in will be same as velocity out.
I think that is physically possible with conventional materials.

1 is for before fulcrum, 2 in the fulcrum and 3 over the fulcrum
David


"An initially stationary object which is allowed to fall freely under gravity drops a distance which is proportional to the square of the elapsed time"
Gravitation - Wikipedia, the free encyclopedia


"In physics, and more specifically kinematics, acceleration is the change in velocity over time."
Acceleration - Wikipedia, the free encyclopedia

[Cloxxki]

A3
B2

The rope was not stated to be massless? They in A, it had potential energy not totally used up in A2. A3 is an exaggeration of the situation, but correct.

B2 seems simplest.

[sebosfato]

A2
B2

because its potential energy will return the same.

[Matos de Matos]

A-3
B-3

Gravity is time dependent and not height dependent.
The velocity attained at the bottom due to gravity will be higher than the velocity lost going up.
The trajectory down is longer, takes more time to travel (longer gravity effect) than the direct trajectory up, and both directions are influenced only by gravity.
Children do that all the time pumping swings.
David
Pumping of a Swing - Physics | Grinnell College

[Cloxxki]

A-3
B-3

Gravity is time dependent and not height dependent.
The velocity attained at the bottom due to gravity will be higher than the velocity lost going up.
The trajectory down is longer, takes more time to travel (longer gravity effect) than the direct trajectory up, and both directions are influenced only by gravity.
Children do that all the time pumping swings.
David
Pumping of a Swing - Physics | Grinnell College

[Armagdn03]

A-3
B-3

Gravity is time dependent and not height dependent.
The velocity attained at the bottom due to gravity will be higher than the velocity lost going up.
The trajectory down is longer, takes more time to travel (longer gravity effect) than the direct trajectory up, and both directions are influenced only by gravity.
Children do that all the time pumping swings.
David
Pumping of a Swing - Physics | Grinnell College

I really hate to leave negative remarks, but this is wrong.

1) Gravity is time and Height dependent, it is an inverse square field.
2) Think in terms of potential energy, a loss less system with such redirection will end up at the same potential it started at.
3) Children parametrically pump their oscillatory system on swings.

If you disagree, perhaps you could show a mathematical proof rather than posting a link to a website, this way people who are not familiar with what you are trying to show will be able to learn and grow, or perhaps you will learn something yourself!

Take care, and thanks for the brain teaser.

[gasman]

1 on both

One of the tricks in this setup is air resistance. Since it is not in a hypothetical vacuum (which, of course, would be just as impossible as the assumptions in this physics puzzle), there will be air resistance. Eventually there will be a terminal velocity reached, and there will be no more acceleration after that point (until something changes... like the ground). Up until terminal velocity is reached, acceleration is velocity/terminal velocity*gravity coefficient. So 2 in both situations is impossible.

The major trick to this thought puzzle, though, is that many who do not know about physics could easily assume that they calculate the length of the dotted line (effectively straightening it), and base bounce height off of that. What someone who chooses 2 or 3 (on either) fails to see is that the dotted line stays the same length the whole time. This rigid line means is that there is only one (theoretical) point at which nearly full gravitational acceleration (approx. 9.8 m/s/s) is achieved (which, in the graphs, is the right-most point). The rest of the time, the gravity affecting the "ball" at any time is a function of the distance from vertical center. Vertical being exactly 0%, and right most being nearly 100%. This also means that, in graph 2, there must be some force added into the system to even begin. The rest of the gravitational force (100%-value from above) is exerted down/through the rigid line, into the fulcrum. So, when compared to a ball simply dropped vertically, this added time will cause much more atmospheric resistance, making the ball's velocity be significantly lower. There are other things, but this is enough to prove that the max bounce height is lower than the original ball height. Since there is only one option less, there is no reason to go further, or do accurate calculations.

[Matos de Matos]

1) Gravity is time and Height dependent, it is an inverse square field.
2) Think in terms of potential energy, a loss less system with such redirection will end up at the same potential it started at.
3) Children parametrically pump their oscillatory system on swings.

Take care, and thanks for the brain teaser.

Parametric oscillator - Wikipedia, the free encyclopedia

[Matos de Matos]

Hi everybody:

I did a simple test with a bucket, a valve and tubing.
This was what I found.
Even against all the friction the water rose over the initial water level, for an instant and then flow back in the tubing to the water level
There is other explanation for this?
On your experiences, did somebody tried to do a collision similar to the quest?

Thank you
David

[Harvey]

Boyles Self Filling Flask.

But I think the answer really is bound to the forces at work. In addition to the gravity being applied to the water in the bucket, you also have air pressure being applied to the entire surface of the water in the bucket, so there is a specific pressure at the valve before it is opened and after it is opened. Now the air total pressure being applied to the outlet opening of the hose is much less than the total pressure being applied to the water in the bucket, because they both have different areas. This is why pressure is measured in terms like Pounds per Square Inch (PSI) or Pascals which are area dependent.

So the process is like this: A pressure is applied to a valve which is opened and a flow of water begins. Since water has mass and a force is pressing on this mass, acceleration occurs. As the water accelerates, it develops kinetic energy in the form of momentum. The path for the moving water is a curved path such that Gravity on the curved path nets to zero - i.e. gains on one side are equally lost on the other so that the net momentum of the moving water is unaffected by gravity from the valve to the hose outlet. Therefore, the only negative restriction to the momentum of the water is the friction in the hose and the air pressure at the outlet.

Once the water leaves the hose, it is subject to the negative effect of the force of gravity and therefore has a finite distance it can travel based on the energy stored in its momentum.

Q1. Could you get an arrangement that would allow the exit stream to re-enter the bucket?

Q2. How different would the experiment be if the hose was filled with water rather than air prior to the experiment.

Q3. How does the answer to Q2 impact continuous operation and how does it demonstrate that extra energy is added to extract the water from the hose?

[Matos de Matos]

Q1. Could you get an arrangement that would allow the exit stream to re-enter the bucket?

Q2. How different would the experiment be if the hose was filled with water rather than air prior to the experiment.

Q3. How does the answer to Q2 impact continuous operation and how does it demonstrate that extra energy is added to extract the water from the hose?

http://www.energeticforum.com/renewa...how-i-see.html

[Cloxxki]

While experimentation is great, I think these relationship are very reliably available described in formulae. I once looked them up for a gravity wheel design, but I'm impossible with formulae, I forget them all.

I don't know the time relationship anymore, but can tell you the end velocity is the same between free fall and 90degree pendulum fall. Just the terminal direction is 90degrees offset. Any difference in speed your experimentation would prove, would allow the simplest gravity design to run indefinitely, and produce excess energy easily harvested.
Inverse direction by the way, offer the same duration and change in velocity, just negative.

[Matos de Matos]

can tell you the end velocity is the same between free fall and 90degree pendulum fall. Just the terminal direction is 90degrees offset.