Is it possible to stop a bullet by just using a magnet?

[jbriggs444]

hah, so in essence, all one needs to do is swing arm very fast and nab the bullet in flight ;)

It's actually easier than that. Just adopt a frame of reference in which the bullet is already at rest.

There's probably a joke in there somewhere. A lawyer, an engineer and a mathematician are blindfolded in front of a firing squad...

 

[Physics_Kid]

It's actually easier than that. Just adopt a frame of reference in which the bullet is already at rest.

There's probably a joke in there somewhere. A lawyer, an engineer and a mathematician are blindfolded in front of a firing squad...

what 'for' would that be?

 

[jbriggs444]

what 'for' would that be?

In what frame of reference is the bullet at rest? The rest frame of the bullet, of course. Not sure what you are trying to ask.

 

[Quandry]

A very simple example can address this question. Electromagnetic dampening is used in balance scales, such as those used for measuring powder charges for 'bullets'.
The balance arm has an aluminium or copper extension which moves within a magnetic field. The effect of this is to dampen the balance arm swing so that it comes to rest faster illustrating that energy is lost from the balance arm as the non magnetic material moves through the magnetic field.

 

[Dr Wu]

The magnetosphere of a neutron star would do a pretty good job at stopping a bullet.

 

[gmalcolm77]

Unfortunately Zachary I strongly disagree as I believe that is not a correct analysis as magnets can do work its just gravity that does no work when an object is at a certain distance to the larger body but since a magnetic field is able to pull a body towards it as work is defined as force * distance in the direction of the force a magnet is by definition is able to do work just check out this site https://van.physics.illinois.edu/qa/listing.php?id=17176 .And on top of that kinetic potential energy is defined as 1/2 mv^2 because this formula includes velocity which is a vector quantity anything that changes the direction of an object and/or the motion therefore changes its kinetic energy. . But my point was that the force needed to stop abullet using a magnet is not achievable right now.

I did the experiment with the magnet moving the aluminum can and all looked good until I replaced the magnet with an unmagnetized bolt and the can still moved due to air displacement, so I think that experiment is bogus unless performed in a vacuum.

 

[Quandry]

I did the experiment with the magnet moving the aluminum can and all looked good until I replaced the magnet with an unmagnetized bolt and the can still moved due to air displacement, so I think that experiment is bogus unless performed in a vacuum.

The experiment and results are based on good science. Your conclusion that it is bogus is based on ...?

 

[thejosh]

The magnetosphere of a neutron star would do a pretty good job at stopping a bullet.

NOW we're talking!

 

[Keith_McClary]

what about lenz law ?

http://www.dingsmagnets.com/industries/aluminum-can-recycling/

When a piece of nonferrous metal, such as aluminum, passes over the separator, the magnets inside the rotor rotate past the aluminum at high speed. This forms eddy currents in the aluminum which in turn create a magnetic field around the piece of aluminum. The polarity of that magnetic field is the same as the rotating magnet, causing the aluminum to be repelled away from the magnet. This repulsion makes the trajectory of the aluminum greater than that of the nonmetallics, allowing the two material streams to be separated.

 

[The Wizard]

Assuming you are 6 ft tall and around 24 inches wide and you have a magnet in front of you that is 6ft. 6" tall and 30 inches wide and about 4 inches thick the magnet should stop the bullet!

In reality a magnet would not work against a plastic or rubber bullet!

 

[Keith_McClary]

Eddy current separator in action:
(1:41 minutes)
(There is also a magnet to separate the ferrous cans at the top of the gadget.)
Another manufacturer states: "It is much more difficult to separate stainless steel, lead ..." presumably due to their lower conductivity and higher density.

 

[Physics_Kid]

who mentioned air moving the item, post #36? ez fix, put can on a very sensitive scale, ug resolution, put it all in a heavy sealed glass box, vacuum it with a automotive AC vacuum. run experiment, see if scale changes when doing test.

 

[mfb]

A sheet of paper between magnet and the can can eliminate air currents nearly completely as well.

 

[gmalcolm77]

The experiment and results are based on good science. Your conclusion that it is bogus is based on ...?

Reference https://www.physicsforums.com/threa...a-bullet-by-just-using-a-magnet.920690/page-2


Just that there is so little resistance to movement of the can, that the displacement of air by the magnet swinging could be causing a slight movement in this experiment. I do not doubt the principle being demonstrated.

 

[gmalcolm77]

who mentioned air moving the item, post #36? ez fix, put can on a very sensitive scale, ug resolution, put it all in a heavy sealed glass box, vacuum it with a automotive AC vacuum. run experiment, see if scale changes when doing test.

A sheet of paper between magnet and the can can eliminate air currents nearly completely as well.

Both excellent suggestions. I'll try the paper or cardboard and repost.