Physics behind Gaussian Accelerator/ Magnetic Linear Accelerator

In summary, the Gaussian accelerator/ Magnetic linear accelerator is an experiment that uses a magnet to transfer momentum to a ball bearing. Different explanations are given on YouTube, but all are based on Newton's 2nd and 3rd law and conservation of energy and momentum.
  • #1
x85247x
3
0
Hi all. i have seen some videos on youtube and i am amazed by the videos of Gaussian accelerator/ Magnetic linear accelerator. As i have a physics project coming up i may consider using this for my project, however i need to ensure that this experiment is within my syllabus. i have basically seen explanations from comments by other people in youtube and i realized there are many different type of explanations from people. Some explanations are * Newton 2nd and 3rd law*, *Conservation of energy, conservation of momentum* and something related to the * Newton's cradle* Base on people explanation, i did check them up on Wikipedia but i can't really seem to understand or confirm my understanding. Thus i hope people here can provide assistance such as provide me with explanation for this experiment.
If there is one, include the laws in explanation.

Below are some Videos that i have watched related to Gaussian accelerator/ Magnetic linear accelerator. (Not mine)

http://www.youtube.com/watch?v=i6JCzkSAc5E&feature=related
http://www.youtube.com/watch?v=epf1AUvG32M&feature=related


All helps are appreciated!
 
Last edited by a moderator:
Physics news on Phys.org
  • #2
This is a nice little science project, but it certainly is not original. Basically a ball bearing is attracted to a strong neodymium-iron magnet, and the momentum at impact is mechanically transferred through the magnet to an equal mass ball bearing on the other side of the magnet that is only weakly attracted to (slowed down by) (restraining force) the magnet due to the two extra ball bearings that act as spacers. So it acts like a momentum multiplier.
 
  • #3
Thanks Bob, but does it include any law in it? Anyone?
 
  • #4
x85247x said:
Thanks Bob, but does it include any law in it? Anyone?
Assume the impulse (momentum integrated over time) from the first ball bearing (BB) is transferred to the second BB with 100% efficiency. This would be true, only if the two BBs have the same mass. If the magnetic force of attraction of the first BB is less than the magnetic force of attraction of the second (true because of the two stationary BBs after magnet), the accelerated BB will have a higher momentum than the first, let's say 20% higher (guess)(1.20 = impulse or momentum multiplier). Then with ten impulse multipliers in a row, the momentum after the last will be 1.20^10 = 6.19 times the first. If this were true, then if the first BB rolled down a 10 cm high slope, then the last one would have 6.19 times the velocity of the first, or 38.34 times as much energy, and should roll up a 383 cm high hill (E = mgh). What we are not completely accounting for is what is the efficiency of the rotational energy transfer. The moment of inertia of a BB is 0.4mR^2 where R is radius, so the total kinetic energy of a rolling BB is 0.5 mv^2 (linear) plus 0.2mv^2 (rotational) = 0.7 mv^2. So there are probably different efficiencies for transferring the linear momentum and the rotational momentum. Your project should explain why the impulse (momentum) is multiplied, and not the energy. Your project should try to measure the rolling momentum transfer multiplier. You should also do the experiment on a greased track so that all the BBs slide instead of roll, and determine the momentum transfer multiplier for sliding BBs.
 
  • #5
Bob S said:
Assume the impulse (momentum integrated over time) from the first ball bearing (BB) is transferred to the second BB with 100% efficiency. This would be true, only if the two BBs have the same mass. If the magnetic force of attraction of the first BB is less than the magnetic force of attraction of the second (true because of the two stationary BBs after magnet), the accelerated BB will have a higher momentum than the first, let's say 20% higher (guess)(1.20 = impulse or momentum multiplier). Then with ten impulse multipliers in a row, the momentum after the last will be 1.20^10 = 6.19 times the first. If this were true, then if the first BB rolled down a 10 cm high slope, then the last one would have 6.19 times the velocity of the first, or 38.34 times as much energy, and should roll up a 383 cm high hill (E = mgh). What we are not completely accounting for is what is the efficiency of the rotational energy transfer. The moment of inertia of a BB is 0.4mR^2 where R is radius, so the total kinetic energy of a rolling BB is 0.5 mv^2 (linear) plus 0.2mv^2 (rotational) = 0.7 mv^2. So there are probably different efficiencies for transferring the linear momentum and the rotational momentum. Your project should explain why the impulse (momentum) is multiplied, and not the energy. Your project should try to measure the rolling momentum transfer multiplier. You should also do the experiment on a greased track so that all the BBs slide instead of roll, and determine the momentum transfer multiplier for sliding BBs.

Thanks a lot BoB!:smile:
 
  • #6
Bob and x85247x,
The physics behind a Gauss Rifle more commonly known as a Magnetic Linear accelerator are a bit more subtle than those described by Newton. Although the magnet does indeed attract the steel ball to it, thereby increasing the velocity of the initial ball which, after the collision, lends to a higher velocity of the fired ball. However if one were to solve the equations of motion, and note the "potential energy" "stored" in the magnetic field one would realize that the velocity of the fired steel ball should only be on the order of 1.25 times that of the initial steel ball, however we know this is not the case as we see in the experiments the velocity of the fired ball is many times that of the initial ball.
The question is where does this extra velocity come from?
The steel ball is a ferrite material which naturally has dipole moments occurring. One can think of the orientation of the dipoles, with respect to the magnetic field ,as stored potential energy. The initial ball has randomized dipole moments, (ie potential energy), as the ball gets closer to the magnetic field the dipoles start to naturally align releasing the potential energy, so in essence when the initial steel ball touches the magnet all the dipoles align with the magnetic field releasing their stored up potential energy.
What's cool about this is because the dipole orientations have natural preferred states with a probability of H/KbT (where H is some constant, Kb is Boltzmann's constant, and T is absolute temperature) through experimentation you should be able to verify that initial hot slow moving balls will produce faster moving fired balls, than cold balls initial balls moving at the same speed. This is because as the temperature of the ball increases the dipole moments within the ball become more randomized, i.e. the stored potential energy increases.
For a more in depth discussion on this I recommend Griffith's intro text on Electromagnetic Theory found here; https://www.amazon.com/dp/013805326X/?tag=pfamazon01-20 or for those more well versed in this topic check of David Jackson's EMT text.
 
Last edited by a moderator:
  • #7
Try doing this experiment with only one steel ball (the recoil ball) on the downstream side of the neodymium magnet and see if the accelerator works. It won't. Now try it with 2 or 3 steel balls on the downstream side. Why does it work with 2 or 3 balls, and not with one? It is because the magnetic binding energy of the second or third ball on the downstream side of the magnet is less than the binding energy of the incident ball on the upstream side of the magnet. Does it depend on the "natural preferred" dipole moment of the incident ball? Probably not.
Bob S
 
  • #8
Bob S said:
Try doing this experiment with only one steel ball (the recoil ball) on the downstream side of the neodymium magnet and see if the accelerator works. It won't. Now try it with 2 or 3 steel balls on the downstream side. Why does it work with 2 or 3 balls, and not with one? It is because the magnetic binding energy of the second or third ball on the downstream side of the magnet is less than the binding energy of the incident ball on the upstream side of the magnet. Does it depend on the "natural preferred" dipole moment of the incident ball? Probably not.
Bob S
I do agree with this post.
In fact the magnets being used are powerful but small which means that most of the energy is very close to the magnet. The incident ball touching receives far more magnetic energy then the projectile loses.
I don’t see how dipole moment comes into it but I could be wrong.
 
  • #9
Per Oni said:
I don’t see how dipole moment comes into it but I could be wrong.
Per Oni-
I agree.
Bob S
 
  • #10
Bob S said:
Assume the impulse (momentum integrated over time) from the first ball bearing (BB) is transferred to the second BB with 100% efficiency. This would be true, only if the two BBs have the same mass. If the magnetic force of attraction of the first BB is less than the magnetic force of attraction of the second (true because of the two stationary BBs after magnet), the accelerated BB will have a higher momentum than the first, let's say 20% higher (guess)(1.20 = impulse or momentum multiplier). Then with ten impulse multipliers in a row, the momentum after the last will be 1.20^10 = 6.19 times the first. If this were true, then if the first BB rolled down a 10 cm high slope, then the last one would have 6.19 times the velocity of the first, or 38.34 times as much energy, and should roll up a 383 cm high hill (E = mgh). What we are not completely accounting for is what is the efficiency of the rotational energy transfer. The moment of inertia of a BB is 0.4mR^2 where R is radius, so the total kinetic energy of a rolling BB is 0.5 mv^2 (linear) plus 0.2mv^2 (rotational) = 0.7 mv^2. So there are probably different efficiencies for transferring the linear momentum and the rotational momentum. Your project should explain why the impulse (momentum) is multiplied, and not the energy. Your project should try to measure the rolling momentum transfer multiplier. You should also do the experiment on a greased track so that all the BBs slide instead of roll, and determine the momentum transfer multiplier for sliding BBs.

Hello Bob, can you please explain why and how

a) "Assume the impulse (momentum integrated over time) from the first ball bearing (BB) is transferred to the second BB with 100% efficiency. This would be true, only if the two BBs have the same mass"

b) "The moment of inertia of a BB is 0.4mR^2 where R is radius, so the total kinetic energy of a rolling BB is 0.5 mv^2 (linear) plus 0.2mv^2 (rotational) = 0.7 mv^2." Here can you explain why 0.4mR^2 becomes 0.2mv^2 (rotational)?
 
  • #11
Vinny_R said:
Bob and x85247x,
The physics behind a Gauss Rifle more commonly known as a Magnetic Linear accelerator are a bit more subtle than those described by Newton. Although the magnet does indeed attract the steel ball to it, thereby increasing the velocity of the initial ball which, after the collision, lends to a higher velocity of the fired ball. However if one were to solve the equations of motion, and note the "potential energy" "stored" in the magnetic field one would realize that the velocity of the fired steel ball should only be on the order of 1.25 times that of the initial steel ball, however we know this is not the case as we see in the experiments the velocity of the fired ball is many times that of the initial ball.
The question is where does this extra velocity come from?
The steel ball is a ferrite material which naturally has dipole moments occurring. One can think of the orientation of the dipoles, with respect to the magnetic field ,as stored potential energy. The initial ball has randomized dipole moments, (ie potential energy), as the ball gets closer to the magnetic field the dipoles start to naturally align releasing the potential energy, so in essence when the initial steel ball touches the magnet all the dipoles align with the magnetic field releasing their stored up potential energy.
What's cool about this is because the dipole orientations have natural preferred states with a probability of H/KbT (where H is some constant, Kb is Boltzmann's constant, and T is absolute temperature) through experimentation you should be able to verify that initial hot slow moving balls will produce faster moving fired balls, than cold balls initial balls moving at the same speed. This is because as the temperature of the ball increases the dipole moments within the ball become more randomized, i.e. the stored potential energy increases.
For a more in depth discussion on this I recommend Griffith's intro text on Electromagnetic Theory found here; https://www.amazon.com/dp/013805326X/?tag=pfamazon01-20 or for those more well versed in this topic check of David Jackson's EMT text.
At what temperatures will this start to actually affect the ball? I did up to 100 degrees C (using basic school equipment) with no change in how much the balls were accelerated (varying from 10x as fast to almost 40).
 

What is a Gaussian Accelerator/Magnetic Linear Accelerator?

A Gaussian Accelerator, also known as a Magnetic Linear Accelerator, is a type of particle accelerator that uses a series of magnets to accelerate charged particles along a linear path. This type of accelerator is used in various scientific and industrial applications, including particle physics research and medical imaging.

How does a Gaussian Accelerator/Magnetic Linear Accelerator work?

A Gaussian Accelerator uses a series of magnets arranged in a specific pattern to create a magnetic field that accelerates charged particles. As the particles pass through the magnetic field, they gain kinetic energy and increase in speed.

What are the advantages of using a Gaussian Accelerator/Magnetic Linear Accelerator?

One of the main advantages of using a Gaussian Accelerator is the ability to accelerate particles to extremely high speeds, close to the speed of light. This allows for the study of particle interactions and behavior at these high energies. Additionally, these accelerators are more compact and cost-effective compared to other types of accelerators, making them useful for a variety of applications.

What are the potential applications of a Gaussian Accelerator/Magnetic Linear Accelerator?

Gaussian Accelerators have a wide range of potential applications, including particle physics research, medical imaging, and industrial processes such as material analysis and testing. They can also be used to create intense beams of charged particles for various purposes, such as producing X-rays for medical imaging.

What are the current challenges facing Gaussian Accelerator/Magnetic Linear Accelerator technology?

One of the main challenges facing Gaussian Accelerator technology is the development of stronger and more efficient magnets. This is necessary to increase the speed and energy of the accelerated particles. Additionally, there is ongoing research to improve the precision and control of the magnetic fields to reduce the effects of beam instabilities and increase the accuracy of particle trajectories.

Similar threads

  • Electromagnetism
Replies
8
Views
763
  • Electromagnetism
Replies
1
Views
1K
  • Electromagnetism
Replies
17
Views
1K
Replies
14
Views
964
Replies
1
Views
1K
Replies
81
Views
23K
  • Classical Physics
Replies
33
Views
1K
Replies
22
Views
1K
Replies
5
Views
845
  • Electromagnetism
Replies
2
Views
971
Back
Top