 # How hard would you have to pull to split ONE atom?

I realize to some extent how strong magnetism is compared to gravity. I know that two pieces of UNmagnetized iron would not jump together as a result of the gravity between them. How do these forces compare with the force that holds nuclei together? (I think that might be called either the weak or the strong force, or a combination) So, could someone pull a single atom apart? How about with a truck? I don’t have much facility with the math, and maybe I’m lost on the concept too? A little help?

I split atoms all the time by passing gas.

Take it with a grain of salt, but the Worst-case scenario people touched on this subject and oddly enough they also could not, like yme, leave fart jokes out of the picture. Great minds think alike :

Ok, from the last site I gather that it would require about a million electronvolts to separate two protons. Can that be equated to any forces that we are acquainted with in daily life? I reiterate - could a couple of trucks develop enough force to do that? trains? battleships?

“could a couple of trucks develop enough force to do that?”

How would you attach both sides of the atom to each truck to pull?

I hope you’re not serious. This is a theoretical question, right?

If the strong force had magnitude of 1 the electromagnetic force would have a magnitude of 1/137 and gravity would equal 6x10[sup]-39[/sup].

If you could somehow separate positive and negative charges, then two one-millimeter particles 30 meters apart would exert a force of three million tons on each other. The strong force is 137 greater than this, but only operates over very short distances.

Electron volts are a measure of the energy in the nuclear bond. With a conversion rate of 1.602x10[sup]-19[/sup] Joule to 1 eV, you would not have to pull very hard to get the protons apart…

To give you a better idea of the energy. 1 kW-hr = 3.60x10[sup]6[/sup] Joules. So 1 MeV = 2.25x10[sup]-20[/sup] kilowatt hours. Sounds easy, right? But how are you going to grab those protons smart guy?

The site uses the figure of 20-30 MeV binding the two protons in a Helium atom.

Given that:
1 eV = 1.60217733 x 10[sup]-19[/sup] J

and using 25 MeV for the binding energy, we get about

4 x 10[sup]-12[/sup] J to separate the protons in a helium atom.

While this is a lot of energy on the atomic scale, it is trivially small macrocropically. Lifting an object that weighs one newton to a height of one meter requires one joule of energy. This is a trillionth of that.

Hopefully, I did the calcs correctly…

What is the magnitude (in coulombs) of those charges you’re using there, Ring?

BTW, I’ve often heard the comparisons stating that gravity is many orders of magnitude weaker than the electromagnetic force, and so on for the weak and strong nuclear forces. (The latter of which is but a residual force of the much stronger color force.)

In any event, aren’t such comparisons akin to comparing apples and oranges? For example, comparing gravity and electromagnetism, one has to assume the masses for the particles in question for the former, and the charges for the particles in question for the latter. Masses and charges; apples and oranges.

It makes perfect sense to compare the (attractive) force due to gravity between two protons to that of the (repulsive) force due to electromagnetism. The latter will be far stronger at any given separation distance. However, I had to assume a pair of particles. One will get a different answer if I had assumed two neutrons, or two uncharged baseballs.

All that being said, when I taught this material, I used to bring in a bar magnet holding up a piece of steel. I would state that “this little magnet is overcoming the gravitational attraction of an entire planet.” This got the idea across of electromagnetism being orders of magnitude stronger than gravity, but again, the comparison always kind of bothered me. (I was comparing the gravitational attraction of two arbitrary masses to the magnetic attraction produced by a bar magnet of arbitrary strength.)

Finally, I’m not going near range considerations for the nuclear forces… You’ll have to ask Richard Feynman the example is on page 2-4 volume 1 of his “The Feynman Lectures on Physics.”

It depends. In Newtonian Mechanics Force just equals mass times accelertion. But when you start getting into GR or QM then the entire concept of force just sorts of fades away.

Ring’s example (taken from Feynman) refers, in technical jargon, to the “coupling strengths” of the various forces. Thus the magnitudes of the charges, masses, nuclear strong force charges, would simply be the relevant quantities for two elementary particles (like a proton) which experience those interactions. Thus, if you compare the gravitational attraction between a proton and a proton and the Coulombic (electromagnetic) repulsion between a proton and a proton, you will find the EM force stronger by a factor of (1/137)/(6 x 10[sup]-39[/sup]).

So you answer your query, robby, the apples-oranges problem isn’t really such a big deal. Ultimately, all these forces originate (and act upon) elementary particles; for these particles, the relatives strengths of the different forces are well defined. Since these elementary particles make up all the matter we see, if makes sense to talk about the relative strengths of these forces in terms of them.