### Author Topic: Conservation of energy/momentum.  (Read 28721 times)

#### chazemz

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##### Re: Conservation of energy/momentum.
« Reply #60 on: 10/15/2017 11:21 am »
Going back to the thought experiment with the magnets. When I am facing the direction of travel and let go of the magnets, as the magnets accelerate towards each other, does their mass increase?

#### meberbs

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##### Re: Conservation of energy/momentum.
« Reply #61 on: 10/15/2017 03:52 pm »
Going back to the thought experiment with the magnets. When I am facing the direction of travel and let go of the magnets, as the magnets accelerate towards each other, does their mass increase?
Rest mass is a constant. Why would you think otherwise?

The relevant speeds are slow enough that relativity is not relevant, so it is not worth bringing in the confusion of relativistic mass, especially given your apparent continued lack of understanding of basic classical physics.

Also, you have completely changed the topic again, are you not interested in understanding why your device is useless?

#### ppnl

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##### Re: Conservation of energy/momentum.
« Reply #62 on: 10/15/2017 04:25 pm »
Going back to the thought experiment with the magnets. When I am facing the direction of travel and let go of the magnets, as the magnets accelerate towards each other, does their mass increase?

No.

You are only converting potential energy into kinetic energy. Thus the energy of the entire system has not changed and so mass has not changed from a relativistic point of view. Which direction you are facing is irrelevant.

If you were to let the magnets collide thus converting the kinetic energy into thermal energy and then let that thermal energy radiate away then the mass of the system would decrease. If you were then to pull the magnets apart thus adding potential energy to the system then their mass would increase.

#### chazemz

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##### Re: Conservation of energy/momentum.
« Reply #63 on: 10/16/2017 11:34 am »
There are some points to think about. With regard to two magnets attracting each other, could anyone advise me on a situation I am thinking about. I am in a small spacecraft that is positioned 50 meters from a space station that I need to get to. I have no engines and it would appear that my situation is hopeless. I do have a basic understanding of classical physics. On board I have two magnets so I hatch a cunning plan. I fix myself to the spacecraft and fix one of the magnets to myself and pull the other magnet away from the one that is attached to me. I know that the magnets attract with equal magnitude and opposite in direction so the spacecraft will not move (see bootstrapping) when I do this. However when I let the magnet go I can now use this attraction to help me. As the free magnet accelerates towards me, due to third law, I and so the spacecraft will move towards the free magnet, reducing the distance between me and the space station by a tiny amount. If I repeat this process many times I am able to reach my destination with no exhaust. So using classical physics it is easy to achieve what some people believe to be impossible?

#### meberbs

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##### Re: Conservation of energy/momentum.
« Reply #64 on: 10/16/2017 02:12 pm »
I fix myself to the spacecraft and fix one of the magnets to myself and pull the other magnet away from the one that is attached to me. I know that the magnets attract with equal magnitude and opposite in direction so the spacecraft will not move
This description is wrong. In order to move the one magnet, you push the outer wall of the spacecraft in the other direction. When the magnets get attracted back together it just moves the spacecraft back to its original position.

A relevant concept is center of mass. The center of mass of the spacecraft plus you plus the magnets will remain stationary unless an external force is applied to the system. Rearranging the mass inside can make the hull shift slightly, but it will shift back upon restoring the mass inside to the original position.

#### ppnl

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##### Re: Conservation of energy/momentum.
« Reply #65 on: 10/16/2017 05:44 pm »
There are some points to think about. With regard to two magnets attracting each other, could anyone advise me on a situation I am thinking about. I am in a small spacecraft that is positioned 50 meters from a space station that I need to get to. I have no engines and it would appear that my situation is hopeless. I do have a basic understanding of classical physics. On board I have two magnets so I hatch a cunning plan. I fix myself to the spacecraft and fix one of the magnets to myself and pull the other magnet away from the one that is attached to me. I know that the magnets attract with equal magnitude and opposite in direction so the spacecraft will not move (see bootstrapping) when I do this. However when I let the magnet go I can now use this attraction to help me. As the free magnet accelerates towards me, due to third law, I and so the spacecraft will move towards the free magnet, reducing the distance between me and the space station by a tiny amount. If I repeat this process many times I am able to reach my destination with no exhaust. So using classical physics it is easy to achieve what some people believe to be impossible?

Actually when you pull the magnets apart the ship will appear to move. This is because you are rearranging the masses around the center of mass. The center of mass will not move but its position relative to the ship will. This will happen even if the objects aren't magnets. All that matters is that you are moving masses.

When you let the magnet go the magnets go back to their starting place and the ship does as well. Again the magnetism does not matter. All that matters is that you are moving masses. You can do it with magnetic fields, springs or air currents. If you move masses the ship will appear to shift. If you move masses back the ship will appear to shift back. What matters is that the center of mass will not shift at all. Ever.

Again the ship will wiggle back and forth by a tiny amount but the center of mass will not move.

#### chazemz

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##### Re: Conservation of energy/momentum.
« Reply #66 on: 10/16/2017 07:14 pm »
The magnets apply equal and opposite forces when they are pulled apart, it is called statics. When I am holding the magnet it is part of my system. When I let it go.It is external to me. You are expending energy to produce baby steps of motion, think of the cannon. The space craft will move and eventually reach the space station.

#### meberbs

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##### Re: Conservation of energy/momentum.
« Reply #67 on: 10/16/2017 07:34 pm »
The magnets apply equal and opposite forces when they are pulled apart, it is called statics. When I am holding the magnet it is part of my system. When I let it go.It is external to me. You are expending energy to produce baby steps of motion, think of the cannon. The space craft will move and eventually reach the space station.
It is not called "statics." Things are moving, which is the opposite of static (the term is dynamics). The simple fact is that to push the magnet away, you and the hull of the spacecraft must move in the opposite direction.

You cannot change the definition of system midway. The magnet is always internal to the spacecraft in this situation.

It has been a while since you have so much as directly addressed a point made by anyone in this thread. Are you actually interested in learning how mechanics works, or are you going to keep repeating incorrect descriptions  while ignoring the correct explanations?

#### ppnl

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##### Re: Conservation of energy/momentum.
« Reply #68 on: 10/16/2017 10:05 pm »
The magnets apply equal and opposite forces when they are pulled apart, it is called statics. When I am holding the magnet it is part of my system. When I let it go.It is external to me. You are expending energy to produce baby steps of motion, think of the cannon. The space craft will move and eventually reach the space station.

Every force has an equal and opposite reaction force. You cannot push on something without it pushing back. If you are floating in mid air and you pull the magnets apart you will not move as the forces cancel out. If you let them pull back together you still will not move and the forces still cancel out. The spaceship around you will not move as it is not connected in any way.

If you are attached to the spaceship and one of the magnets is also then when you pull the magnets apart the spaceship will move. Even if the objects you use aren't magnetic and you pull them apart the ship will move. It makes no difference if there is a magnetic field, spring, rubber band or nothing at all. All you are doing is changing the center of mass of the ship by moving the massive objects. All you can do is make the ship wiggle back and forth by a tiny amount as you move the masses apart and back together. All you are doing is shifting the ship with respect to its center of mass.

You only have an intuitive grasp of mechanics and your intuition is just wrong. The cannon example shows how bad you have it wrong. The cannon is attached to the Earth so when you fire the cannon in one direction it shoves the entire earth in the other by a tiny amount. When the cannon ball hits the earth it cancels the motion of the cannon and the tiny motion of the Earth. Both are in different positions now. The Earth has moved by only a tiny amount. When you carry the cannon ball back to the cannon you drag the Earth back to its original position as well. In the end everything is back where it started. And just like with the space ship you have only moved the Earth with respect to the center of mass of the Earth ball system. The center of mass did not change at all as the Earth wiggles back and forth.

#### Bob012345

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##### Re: Conservation of energy/momentum.
« Reply #69 on: 10/17/2017 06:17 pm »
There are some points to think about. With regard to two magnets attracting each other, could anyone advise me on a situation I am thinking about. I am in a small spacecraft that is positioned 50 meters from a space station that I need to get to. I have no engines and it would appear that my situation is hopeless. I do have a basic understanding of classical physics. On board I have two magnets so I hatch a cunning plan. I fix myself to the spacecraft and fix one of the magnets to myself and pull the other magnet away from the one that is attached to me. I know that the magnets attract with equal magnitude and opposite in direction so the spacecraft will not move (see bootstrapping) when I do this. However when I let the magnet go I can now use this attraction to help me. As the free magnet accelerates towards me, due to third law, I and so the spacecraft will move towards the free magnet, reducing the distance between me and the space station by a tiny amount. If I repeat this process many times I am able to reach my destination with no exhaust. So using classical physics it is easy to achieve what some people believe to be impossible?

There are a few ways I can think of to get back to the station using the magnets. If you had a 50m+ string you could throw one of the magnets to the station and hope it attaches. Then you can gently pull yourself towards it. But in the whole process, the center of mass remains stationary. Or, you could throw both magnets in the opposite direction to gain a small velocity towards the station but the center of mass still remains stationary. Or, if you're truly doomed, you could break one of the magnets to make a sharp edge and then poke a small hole in your spacesuit and use the escaping air as a rocket to close the gap yet even then the center of mass remains stationary! But you need to be quick about getting back.
« Last Edit: 10/17/2017 06:21 pm by Bob012345 »

#### chazemz

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##### Re: Conservation of energy/momentum.
« Reply #70 on: 10/18/2017 01:16 pm »
Going back to the thought experiment with the magnets. When I am facing the direction of travel and let go of the magnets, as the magnets accelerate towards each other, does their mass increase?

No.

You are only converting potential energy into kinetic energy. Thus the energy of the entire system has not changed and so mass has not changed from a relativistic point of view. Which direction you are facing is irrelevant.

If you were to let the magnets collide thus converting the kinetic energy into thermal energy and then let that thermal energy radiate away then the mass of the system would decrease. If you were then to pull the magnets apart thus adding potential energy to the system then their mass would increase.
In the first instance you are expending energy and storing it as potential energy, so yes.

#### chazemz

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##### Re: Conservation of energy/momentum.
« Reply #71 on: 10/18/2017 01:23 pm »
The magnets apply equal and opposite forces when they are pulled apart, it is called statics. When I am holding the magnet it is part of my system. When I let it go.It is external to me. You are expending energy to produce baby steps of motion, think of the cannon. The space craft will move and eventually reach the space station.

Every force has an equal and opposite reaction force. You cannot push on something without it pushing back. If you are floating in mid air and you pull the magnets apart you will not move as the forces cancel out. If you let them pull back together you still will not move and the forces still cancel out. The spaceship around you will not move as it is not connected in any way.

If you are attached to the spaceship and one of the magnets is also then when you pull the magnets apart the spaceship will move. Even if the objects you use aren't magnetic and you pull them apart the ship will move. It makes no difference if there is a magnetic field, spring, rubber band or nothing at all. All you are doing is changing the center of mass of the ship by moving the massive objects. All you can do is make the ship wiggle back and forth by a tiny amount as you move the masses apart and back together. All you are doing is shifting the ship with respect to its center of mass.

You only have an intuitive grasp of mechanics and your intuition is just wrong. The cannon example shows how bad you have it wrong. The cannon is attached to the Earth so when you fire the cannon in one direction it shoves the entire earth in the other by a tiny amount. When the cannon ball hits the earth it cancels the motion of the cannon and the tiny motion of the Earth. Both are in different positions now. The Earth has moved by only a tiny amount. When you carry the cannon ball back to the cannon you drag the Earth back to its original position as well. In the end everything is back where it started. And just like with the space ship you have only moved the Earth with respect to the center of mass of the Earth ball system. The center of mass did not change at all as the Earth wiggles back and forth.

If the magnet is attracted to you, then you are attracted to the magnet, think force pairing. Yes, you are correct, when you pull the magnets apart the forces will cancel out.
I placed the cannon in a spacecraft so cannot comment further on this.
One error though, I think it incorrect to use the word "external" as you are still connected by the flux lines.

#### chazemz

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##### Re: Conservation of energy/momentum.
« Reply #72 on: 10/18/2017 01:38 pm »
There are some points to think about. With regard to two magnets attracting each other, could anyone advise me on a situation I am thinking about. I am in a small spacecraft that is positioned 50 meters from a space station that I need to get to. I have no engines and it would appear that my situation is hopeless. I do have a basic understanding of classical physics. On board I have two magnets so I hatch a cunning plan. I fix myself to the spacecraft and fix one of the magnets to myself and pull the other magnet away from the one that is attached to me. I know that the magnets attract with equal magnitude and opposite in direction so the spacecraft will not move (see bootstrapping) when I do this. However when I let the magnet go I can now use this attraction to help me. As the free magnet accelerates towards me, due to third law, I and so the spacecraft will move towards the free magnet, reducing the distance between me and the space station by a tiny amount. If I repeat this process many times I am able to reach my destination with no exhaust. So using classical physics it is easy to achieve what some people believe to be impossible?

There are a few ways I can think of to get back to the station using the magnets. If you had a 50m+ string you could throw one of the magnets to the station and hope it attaches. Then you can gently pull yourself towards it. But in the whole process, the center of mass remains stationary. Or, you could throw both magnets in the opposite direction to gain a small velocity towards the station but the center of mass still remains stationary. Or, if you're truly doomed, you could break one of the magnets to make a sharp edge and then poke a small hole in your spacesuit and use the escaping air as a rocket to close the gap yet even then the center of mass remains stationary! But you need to be quick about getting back.

The rules of the game were that nothing leaves the spacecraft, so on a technical point I cannot award you any marks. However thought experiments are designed to make you think and you have certainly done this. So I am going to award you two bonus marks for effort.
On a more serious note, By using third law you can use the potential energy of the stretched flux lines as they contract to move an object from within. The time of the movement is very short but the device overcomes this time constraint. I have copied my words from the earlier thread so people can compare them with the video .

The rotor arm magnet rotates into the repelling magnet field of the body magnet. As the distance between the two magnets decreases, the repelling force will increase. The repelling force of the body magnet will act upon the rotor arms, causing them to decelerate which can easily be seen on the video. If we apply third law, the rotor arm magnet must therefore apply the same increasing repelling force on the body magnet. This repelling force must therefore restrict the body's attempts to counter rotate. Since the body/stator is applying the load to the rotor arms/armature then the body cannot counter rotate.  We are at the point where the rotor arm has just enough momentum left to move across the body magnet. The magnetic potential energy in the body magnet and the rotor magnet is released and the rotor magnet is accelerated down the tube, which you can hear on the video. The motor is now free to accelerate and again, using classical physics, we know what should happen. As the rotor arms accelerate a force should be applied to the body causing the body to counter rotate. But as you can see in the video, the body does not counter rotate. This means that there is a counter force acting on the body which stops it counter rotating. There is a slight oscillation in the body but, if we refer to the slinky experiment, we can use statics to explain this process.
So, as the magnets are forced together, load is applied to the motor. If we look at armature reaction, we will see that, due to the load, the main field flux lines will distort and shift the Magnetic Neutral Axis in the opposite direction to rotation. As stated earlier, the body cannot move since it is effectively pushing against itself. It is easier to visualize the movement of the M.N.A so that when the tube magnet accelerates down the tube, load will rapidly drop which will cause the main field flux lines to shorten and the M.N.A will now move in the direction of rotation. This will drag the body in the direction of rotation.

We now have the required situation where the body is attempting to move in the direction of rotation. At the same time the rotor arms apply the counter force as they accelerate.

So there you have it. A very simple device. Everything that has been explained is known and can be easily accessed. All the information can be easily found on the internet  or in any electrical engineering textbook.
I will go through the video in detail :-
1) The body is at rest and the nearest tube magnet has been pushed down the tube to allow for starting.
2) Power is switched on, the rotor arms accelerate and the body counter-rotates, winding the string.
3) Jerk cycle takes effect, resulting in no counter-rotation of the body.
4) The string now unwinds, so the device swings back and forth (string winding and unwinding) until it returns to its rest position (i.e. string is not wound).
5) Transfer of momentum as observed, device moves in the direction of the rotor arms.

If you turn the power off when the device has returned to its rest position at exactly the moment the tube magnet begins to accelerate down the tube when facing the body magnet, the device will not move, so there is no stored energy in the string at this point.

#### meberbs

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##### Re: Conservation of energy/momentum.
« Reply #73 on: 10/18/2017 03:05 pm »
Going back to the thought experiment with the magnets. When I am facing the direction of travel and let go of the magnets, as the magnets accelerate towards each other, does their mass increase?

No.

You are only converting potential energy into kinetic energy. Thus the energy of the entire system has not changed and so mass has not changed from a relativistic point of view. Which direction you are facing is irrelevant.

If you were to let the magnets collide thus converting the kinetic energy into thermal energy and then let that thermal energy radiate away then the mass of the system would decrease. If you were then to pull the magnets apart thus adding potential energy to the system then their mass would increase.
In the first instance you are expending energy and storing it as potential energy, so yes.
You are not "expending energy" you are changing the form of the energy. Energy in the system is constant. Also, I do not know what you mean by "first instance" because only one situation was described, and contrary to your most recent post, it starts with potential energy and converts it to kinetic.

On a more serious note, By using third law you can use the potential energy of the stretched flux lines as they contract to move an object from within.
False. You cannot move an object from within except to shift the mass distribution around the stationary center of mass, and neither magnetic field lines nor any form of energy have anything to do with this.

The time of the movement is very short but the device overcomes this time constraint.
The constraint is simply that the center of mass does not move, and there is no overcoming this constraint.

The rotor arm magnet rotates into the repelling magnet field of the body magnet. As the distance between the two magnets decreases, the repelling force will increase. The repelling force of the body magnet will act upon the rotor arms, causing them to decelerate which can easily be seen on the video. If we apply third law, the rotor arm magnet must therefore apply the same increasing repelling force on the body magnet. This repelling force must therefore restrict the body's attempts to counter rotate.
It does not "restrict the body's attempts to counter rotate." It simply transfers angular momentum from the arms to the body. The body already is rotating the opposite direction of the arms with equal magnitude of angular momentum. The action of the magnets slows down both the arms and the body, reducing the amount of angular momentum in both by the same amount. This interaction does not change the total angular momentum in the arms plus the body from 0.

I will stop pointing out the wrong things in your description here, because what you have said so far is so wrong, the rest ceases to have any meaning.

So there you have it. A very simple device.
Yes, it is a relatively simple device, so it is strange that you continue to make such completely wrong statements about it.

Everything that has been explained is known and can be easily accessed. All the information can be easily found on the internet  or in any electrical engineering textbook.
Yes, what is needed to understand your device is easily available, but you seem to have not read any of it. For example, you keep using the word "force" when you should be using the word "torque."

I will go through the video in detail :-
1) The body is at rest and the nearest tube magnet has been pushed down the tube to allow for starting.
2) Power is switched on, the rotor arms accelerate and the body counter-rotates, winding the string.
Good so far

3) Jerk cycle takes effect, resulting in no counter-rotation of the body.
Not "no counter rotation of the body", but a balance between the torque applied by the motor and the opposite torque applied by the magnets, so that the relative rotation speed between the arms and body is roughly fixed (if you average out the jerks)

A simpler way to accomplish the same thing without the magnets is either use a motor designed to operate at a fixed slower speed, or to apply less power to the motor so that its internal friction limits its speed to a lower value.

4) The string now unwinds, so the device swings back and forth (string winding and unwinding) until it returns to its rest position (i.e. string is not wound).
You keep ignoring that during this step, the string applies a torque to the body. The body transfers some of this angular momentum to the arms, maintaining the rotational speed difference that balances the effect of the arms and the motor.

5) Transfer of momentum as observed, device moves in the direction of the rotor arms.
This angular momentum originally came from the torques applied by the string.

Edit: fix quote tags
« Last Edit: 10/18/2017 05:35 pm by meberbs »

#### chazemz

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##### Re: Conservation of energy/momentum.
« Reply #74 on: 10/18/2017 03:32 pm »
You cannot have things both ways, either classical physics is correct or it is wrong. When I let go of the magnet will I be attracted to it as it is attracted to me?

#### Bob012345

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##### Re: Conservation of energy/momentum.
« Reply #75 on: 10/18/2017 05:32 pm »
You cannot have things both ways, either classical physics is correct or it is wrong. When I let go of the magnet will I be attracted to it as it is attracted to me?

Still not clear what you are trying to achieve. Are you claiming to generate more rotational energy than the energy you put into the device? Can you plainly state in one simple sentence what the device is supposed to do?

#### meberbs

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##### Re: Conservation of energy/momentum.
« Reply #76 on: 10/18/2017 05:44 pm »
You cannot have things both ways, either classical physics is correct or it is wrong. When I let go of the magnet will I be attracted to it as it is attracted to me?
Classical physics is correct. You keep describing things contrary to classical physics though.

You are the one trying to have it both ways. You want to be attracted to the magnet as it is attracted to you (which you are), but you want to ignore that when you push the magnet away from you, you get pushed back as well. You are applying a force to the magnet greater than the attraction between the 2 magnets to push it away. This means by Newton's third law that it applies an equal and opposite force on you which is therefore also greater than the force of attraction, making you move away as well (to rephrase for clarity, you move in the opposite direction as the direction you pushed magnet).

#### chazemz

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##### Re: Conservation of energy/momentum.
« Reply #77 on: 10/18/2017 07:05 pm »
You cannot have things both ways, either classical physics is correct or it is wrong. When I let go of the magnet will I be attracted to it as it is attracted to me?
Classical physics is correct. You keep describing things contrary to classical physics though.

You are the one trying to have it both ways. You want to be attracted to the magnet as it is attracted to you (which you are), but you want to ignore that when you push the magnet away from you, you get pushed back as well. You are applying a force to the magnet greater than the attraction between the 2 magnets to push it away. This means by Newton's third law that it applies an equal and opposite force on you which is therefore also greater than the force of attraction, making you move away as well (to rephrase for clarity, you move in the opposite direction as the direction you pushed magnet).

Nice try, you have changed pull to push. You need to think about what you are proposing. If by pulling the magnets apart I generate a force in the opposite direction, by holding the magnet away from me there would be no opposing force so the spacecraft would glide over to the space station or carry on into the great unknown. How can equal and opposite be greater on one side?

#### meberbs

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##### Re: Conservation of energy/momentum.
« Reply #78 on: 10/18/2017 07:48 pm »
You cannot have things both ways, either classical physics is correct or it is wrong. When I let go of the magnet will I be attracted to it as it is attracted to me?
Classical physics is correct. You keep describing things contrary to classical physics though.

You are the one trying to have it both ways. You want to be attracted to the magnet as it is attracted to you (which you are), but you want to ignore that when you push the magnet away from you, you get pushed back as well. You are applying a force to the magnet greater than the attraction between the 2 magnets to push it away. This means by Newton's third law that it applies an equal and opposite force on you which is therefore also greater than the force of attraction, making you move away as well (to rephrase for clarity, you move in the opposite direction as the direction you pushed magnet).

Nice try, you have changed pull to push.
I changed nothing, but you seem to have no idea what the words you are using mean.

Pull and push both mean "apply a force to." Pull would be applying a force towards you, and push would be applying a force away from you. In the situation you have described, both you and "magnet A" are attached to the wall of your ship. You described moving "magnet B" away from you, the general term to describe this direction is push. I ignored your contradictory use of the word pull, since the direction is obvious, and the only other part is the same for both push and pull, you are applying a force.

If by pulling the magnets apart I generate a force in the opposite direction, by holding the magnet away from me there would be no opposing force so the spacecraft would glide over to the space station or carry on into the great unknown. How can equal and opposite be greater on one side?

You need to think about what you are saying, or maybe just go take an introductory physics course.

You are the one that is saying that "equal and opposite are greater on one side." Since the forces are equal and opposite, how could you move anywhere?

If you hold the magnet out at arm's length, there are 4 forces at play. Magnet A is attracting magnet B. Magnet B is attracting magnet A (opposite direction). You are applying a contact force to magnet B pushing it away from you, countering its attraction to magnet A. Magnet B applies an equal and opposite contact force on you, countering the magnetic force that otherwise would pull magnet A (along with you and the spacecraft) towards magnet B. Nothing is moving.

Starting from the position with the magnets touching, to separate them, you apply a force to move magnet B away, which in turn makes you move in the opposite direction as well. You continue to apply a force that balances the magnetic attraction to keep magnet B moving away, and you moving away from magnet B. (Balanced forces at this point so no acceleration, just constant velocity motion.) When you reach arm's length, you briefly stop applying this force to allow the magnetic attraction between A and B to stop you from moving further from B and B from moving further from you. (Possibly you apply a force in the opposite direction than you had been to bring you and magnet B to rest faster). Once you have done this, neither you nor magnet B are moving and you are in the static situation I described above.

To probably save some unnecessary back and forth: Do not use the word energy in replying to this post. Energy is not relevant to this description, only forces and momentum. I could describe the energy in this situation, but it is irrelevant and a distraction if you don't first understand what I have said here.

#### chazemz

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##### Re: Conservation of energy/momentum.
« Reply #79 on: 10/20/2017 02:42 pm »

To probably save some unnecessary back and forth: Do not use the word energy in replying to this post. Energy is not relevant to this description, only forces and momentum. I could describe the energy in this situation, but it is irrelevant and a distraction if you don't first understand what I have said here.

[/quote]

Energy is NEVER irrelevant.

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