# VARIPEND

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Posted (edited)

Let me introduce for your attention a very interesting mechanical system.

It is called: "Varipend." Variable pendulum ( VariPend = VARIable + PENDulum)

A pendulum of variable length and mass, implemented in an isolated system.

- the case increases its mass
- working moving mass decreases

The mass of the entire system is unchanged!

$M(t) = {m_{liquid}}(t) + {m_{case}}(t) = const$

The total momentum of the Varipend system:

${{\vec p}_{var}}(t) = {m_{liquid}}(t)\;{{\vec v}_1}(t) + {m_{case}}(t)\;{{\vec v}_2}(t)$

In Mechanics, there is a Law of Conservation of Momentum (LCM):

Which states that the TOTAL MOMENTUM of the mechanical system - without external forces - IS STABLE.

Quote

The law of conservation of momentum

The law of conservation of momentum states that the total momentum (vector sum of the momenta of all the bodies of the system) is a constant, if the vector sum of the external forces acting on the system of bodies is zero.

$\vec P(t)=\sum {{m_i}(t){{\dot r}_i}(t)}=const$

$\frac{d\vec P(t)}{dt}=\frac{d(\sum{{m_i(t)}{\dot r_i(t)}})}{dt}=\sum {{m_i}{\ddot r_i}}+\sum{{\dot m_i}{\dot r_i}}=0$
if $F^e=0$

Here is this system, in this form:

The total momentum is LINK DELETED !

This suggests that “external forces” act on this system in this form!

If you release the system from external influences, then the LINK DELETED of this system will look like this:

This is a simple solution to a LINK DELETED!

${p_{var}}(t) = {m_{liquid}}(t){{\vec v}_1}(t) + {m_{case}}(t){{\vec v}_2}(t) = 0$

Quote

If at any moment in time the relative movement of the system of moving elements is stopped, the entire mechanical system will have an initial speed.

If at the initial moment of time the entire mechanical system had zero speed in the system ... then after stopping the system of moving elements the speed of the entire mechanical system will also be zero!

The graph of the total momentum of the system.

You can explore the same mechanical system by solving the LINK DELETED

This solution is using a mechanical Lagrangian :

Quote

LINK DELETED also shows the possibility of moving a closed mechanical system without external influence.

Red color indicates the trajectory of the center of mass of the entire system  LINK DELETED,

Blue color - case movement LINK DELETED.

===============================

Before you is the law of conservation of momentum and the law of conservation of energy!

In pure form!

===============================

This task is not mathematically complicated.
But she is very, very difficult in terms of psychology ....

Edited by Strange

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Hw does the center remain fixed when the ball moves away from it (and again toward it)? You are violating conservation of momentum in your animation, so it's no wonder you conclude that momentum isn't conserved. You have a force on the ball, but you aren't acknowledging it. Or you are essentially assuming an infinite mass is connected at the center. Put another way, you are showing an accelerating reference frame, not an inertial one, so Newton's laws can't be applied. Pick your poison.

Show me a real system that acts this way and we can talk.

51 minutes ago, butovsv said:

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1 hour ago, butovsv said:

An analysis of the motion of a mechanical system using the Lagrange equations also shows the possibility of moving a closed mechanical system without external influence.

That sounds like a reactionless drive? Given that such things are impossible when current laws of physics (Newton, Lagrange, Hamilton etc) are correctly used we can safely assume that the Lagrange equations are incorrectly used in the analysis. If you have discovered new physics where current laws does not apply, please post references/evidence, that would be interesting to discuss!

!

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On 8/15/2019 at 2:10 PM, swansont said:

Hw does the center remain fixed when the ball moves away from it (and again toward it)? You are violating conservation of momentum in your animation, so it's no wonder you conclude that momentum isn't conserved.

The total momentum of this system is Zero.
It is no more and no less than zero - it is strictly equal to Zero!

${p_{var}}(t) = {m_{liquid}}(t){\vec v_1}(t) + {m_{case}}(t){\vec v_2}(t) = 0$

There is no other solution!

There is no other law of conservation of momentum!

On 8/15/2019 at 2:10 PM, swansont said:

Show me a real system that acts this way and we can talk

A VARIPEND is any centrifugal pump operating in the mode of periodically breaking the flow of a pumped substance.

On 8/15/2019 at 2:55 PM, Ghideon said:

Given that such things are impossible when current laws of physics (Newton, Lagrange, Hamilton etc)

What “such things” are not possible under conservation laws?

If you see the Center of Mass of this pretty mechanical system and you see it clearly, then this CM violates the "conservation laws" that are obvious to you, then you need to contact your psychotherapist immediately - he will help you cure not only your eyesight!

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30 minutes ago, butovsv said:

What ﻿“such things” are not possible under conservation laws?﻿﻿

Such things= mechanical devices claiming to produce propulsion without external force. Also known as reactionless drive.

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49 minutes ago, Ghideon said:

Such things= mechanical devices claiming to produce propulsion without external force. Also known as reactionless drive. ﻿

Lets, remember Physics! Its basic concepts!

What do "external forces" change?
What can not change the system of material bodies without "external force"?

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18 minutes ago, butovsv said:

Yes.

19 minutes ago, butovsv said:

Let's remember Physics! Its basic﻿﻿﻿﻿﻿﻿﻿﻿﻿﻿﻿﻿﻿﻿﻿﻿﻿﻿ concepts﻿﻿﻿﻿﻿!﻿

Agreed, you should do that.

20 minutes ago, butovsv said:

Wha﻿t﻿ do "external force﻿s﻿﻿﻿﻿﻿﻿﻿" cha﻿nge﻿?﻿

Velocity for one.

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Posted (edited)
1 hour ago, Bufofrog said:
1 hour ago, butovsv said:

Wha﻿t﻿ do "external force﻿s﻿﻿﻿﻿﻿﻿﻿" cha﻿nge﻿?﻿

Velocity for one. ﻿

No!

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A modern statement of Newton's Second Law is a vector equation:[Note 1]

$\vec F = \frac{{{\rm{d}}\vec p}}{{{\rm{d}}t}}$

where ${\vec p}$ is the momentum of the system, and ${\vec F}$ is the net (vector sum) force. If a body is in equilibrium, there is zero net force by definition (balanced forces may be present nevertheless). In contrast, the second law states that if there is an unbalanced force acting on an object it will result in the object's momentum changing over time.[9]

By the definition of momentum,

$\vec F = \frac{{{\rm{d}}\vec p}}{{{\rm{d}}t}} = \frac{{{\rm{d}}\left( {m\vec v} \right)}}{{{\rm{d}}t}}$

where m is the mass and ${\vec v}$ is the velocity.[3]:9-1, 9-2

For one material object of constant mass:

$\frac{{d\vec p}}{{dt}} = \frac{{d(m\vec v)}}{{dt}} = m\frac{{d\vec v}}{{dt}} = m\vec a$

For one material object of variable mass:

$\frac{{d\vec p}}{{dt}} = \frac{{d(m\vec v)}}{{dt}} = m\frac{{d\vec v}}{{dt}} + {v_r}\frac{{dm}}{{dt}} = m\vec a + {{\vec F}^j}$

1 hour ago, Bufofrog said:

Velocity for one. ﻿

momentum - is NOT velocity
change in momentum - is NOT a change in velocity
the immutability of the momentum - is NOT the immutability of velocity!

Edited by butovsv

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3 hours ago, butovsv said:

3 hours ago, butovsv said:

pvar(t)=mliquid(t)v⃗ 1(t)+mcase(t)v⃗ 2(t)=0

The momentum in the above animation is not zero. Animations aren't enough to demonstrate anything, since they need not obey the laws of physics.

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20 minutes ago, swansont said:

Posting the same animation doesn't answer my question about the animation. ﻿

We’ll fix it right now!

Here is this system, in this form:

The total momentum is LINK DELETED AGAIN

This suggests that “external forces” act on this system in this form!

If you release the system from external influences, then the LINK DELETED AGAIN   of this system will look like this:

20 minutes ago, swansont said:

The momentum in the above animation is not zero. Animations aren't enough to demonstrate anything, since they need not obey the laws of physics.

Did you define it "by eye"?

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18 minutes ago, butovsv said:

No!

For one material object of constant mass:

dp⃗ dt=d(mv⃗ )dt=mdv⃗ dt=ma⃗

And if something accelerates, its velocity changes. By definition.

18 minutes ago, butovsv said:

momentum - is NOT velocity
change in momentum - is NOT a change in velocity
the immutability of the momentum - is NOT the immutability of velocity!

One way to change momentum is to change velocity. It strains credulity to think you are objecting to this.

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17 minutes ago, swansont said:

since they need not obey the laws of physics.﻿

What law of Physics are you trying to protect with your breasts now?

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6 minutes ago, butovsv said:

We’ll fix it right now!

Here is this system, in this form:

The total momentum is LINK DELETED AGAIN

This suggests that “external forces” act on this system in this form!

Yes, as I had implied. There must be a force acting on the system for it to behave like that. There is no application of conservation of momentum.

Quote

Did you define it "by eye"?

The center of mass is moving to the right. Momentum is not going to be zero.

!

Moderator Note

Your links were removed for a reason — they violate our rules on advertising (see rule 2.7 in the guidelines). Don't put them in again, or you will be banned as a spammer. Whatever you want to discuss needs to happen here, on this site.

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Just now, swansont said:

And if something accelerates, its velocity changes. By definition.

A brick?

$R = \frac{1}{M}\mathop \sum \limits_{i = 1}^n {m_i}{r_i}$

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Just now, butovsv said:

A brick?

R=1Mi=1nmiri

I don't understand your objection. If I change the momentum of the brick, its velocity will change. Thus, velocity is an example of something that can change when there is an external force. And for a system of constant mass, it must change.

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2 minutes ago, swansont said:

Moderator Note

Your links were removed for a reason — they violate our rules on advertising (see rule 2.7 in the guidelines). Don't put them in again, or you will be banned as a spammer. Whatever you want to discuss needs to happen here, on this site. ﻿

We’ll fix it right now!

Here is this system, in this form:

The total momentum is LINK DELETED CHANGING !

This suggests that “external forces” act on this system in this form!

If you release the system from external influences, then the LINK DELETED  CONSTANT TOTAL MOMENTUM of this system will look like this:

This is a simple solution to a First Order Differential Equation:

${p_{var}}(t) = {m_{liquid}}(t){{\vec v}_1}(t) + {m_{case}}(t){{\vec v}_2}(t) = 0$

!

pvar(t)=mliquid(t)v⃗ 1(t)+mcase(t)v⃗ 2(t)=0﻿

2 minutes ago, swansont said:

I don't understand your objection. If I change the momentum of the brick, its velocity will change. Thus, velocity is an example of something that can change when there is an external force. And for a system of constant mass, it must change.

With a brick, everything is clear even to a schoolboy.
More precisely, the student does not know anything except the brick!

Now please change the momentum of the system of bodies.

For example, brick systems!

Such a system, where many, many bricks!

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6 minutes ago, butovsv said:

We’ll fix it right now!

Here is this system, in this form:

The total momentum is LINK DELETED CHANGING !

This suggests that “external forces” act on this system in this form!

Yes. I will ask again: what are the forces?

Quote

If you release the system from external influences, then the LINK DELETED  CONSTANT TOTAL MOMENTUM of this system will look like this:

No, if the momentum remained constant, the center of mass would not move.

How do you get the ball to do what it does without external forces?

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Posted (edited)
32 minutes ago, swansont said:

Yes. I will ask again: what are the forces? ﻿

This force is equal to the change in the momentum of the moving substance moving along the trajectory.

32 minutes ago, swansont said:

No, if the momentum remained constant, the center of mass would not move.

How do you get the ball to do what it does without external forces?

hM-m-m......

CENTER Mass of the body system is associated with the total momentum?

How long ago?

Can you write an equation to calculate the center of mass of a system of bodies?

Can you write an equation that allows you to calculate the SUM MOMENTUM of all the bodies in the system?

Can you write the equation of CHANGE in the total momentum of a system of bodies?
Those. just differentiate the total momentum?

Edited by butovsv

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3 hours ago, butovsv said:

Lets﻿﻿﻿, remem﻿ber Physics! Its basic co﻿ncepts!﻿﻿

﻿ What do "externa﻿l forces" change?
What can not ﻿change the system of material bodies without "external﻿ f﻿o﻿r﻿ce﻿"﻿﻿?

Ok. Let’s make sure we discuss the same thing.

A body with mass=m is at rest in our frame of reference, in vacuum in free space. There are no external forces acting on the body; the sum of forces acting is = 0. According to Newton the equation F=ma describes the situation; how the object will accelerate. Since force F=0 then acceleration a=0. Are you claiming that you have found a way to make a body accelerate even when F=0?

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1 minute ago, Ghideon said:

Ok. Let’s make sure we discuss the same thing.

A body with mass=m is at rest in our frame of reference, in vacuum in free space. There are no external forces acting on the body; the sum of forces acting is = 0. According to Newton the equation F=ma describes the situation; how the object will accelerate. Since force F=0 then acceleration a=0. Are you claiming that you have found a way to make a body accelerate even when F=0?  ﻿

Body?!

Who said "BODY"?

Look again carefully!

What do you see?

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21 minutes ago, butovsv said:

Who﻿ said﻿ "BODY"?

I did. I’m trying to understand what you are proposing. So I try to use words commonly used in scientific discussions. Put your rig inside a hollow sphere and call the complete assembly ”body” if that helps define an answer.

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2 minutes ago, Ghideon said:
31 minutes ago, butovsv said:

Who﻿ said﻿ "BODY"?

I did. I’m trying to understand what you are proposing. So I try to use words commonly used in scientific discussions. Put your rig inside a hollow sphere and call the complete assembly ”body” if that helps define an answer.﻿

Oh well!

35 minutes ago, Ghideon said:

A body with mass=m is at rest in our frame of reference, in vacuum in free space. There are no external forces acting on the body; the sum of forces acting is = 0. According to Newton the equation F=ma describes the situation; how the object will accelerate. Since force F=0 then acceleration a=0. Are you claiming that you have found a way to make a body accelerate even when F=0?

Look carefully again!

Does the mass of the “body” change?
On the “case”, does the “force” act?

How will the “body-case” behave if it is allowed to move in its own way?

What will the constant total momentum of this system look like in the absence of external forces?

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3 minutes ago, butovsv said:

Look﻿ carefully aga﻿in!﻿﻿﻿

Try answering questions instead of posting new questions. What will happen according to you? Will there be acceleration a>0 even if F=0?

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9 minutes ago, Ghideon said:

Try answering questions instead of posting new questions. What will happen according to you? Will there be acceleration a>0 even if F=0?  ﻿﻿﻿﻿﻿

Look﻿ carefully aga﻿in!

The momentum of the moving substance changes

The change in momentum is called "force."

The force acts on the" body-case".

If the "body-case" is freed from external retention, the "body-case" will move with acceleration!

The change in the momentum of the "body-case", increasing its mass, will be equal to the change in the momentum of the moving mass.

================================================================

once more!

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