Definition of forces

Question

In my physics textbook, while talking about the scope of physics, it mentions the four fundamental forces of nature which are Gravitational force, Electromagnetic force, Strong Nuclear force and Weak Nuclear force, of these the most astonishing one I feel is the weak nuclear force. My book states that it is responsible for $\beta$-decay and other kinds of radioactivity. Now as far as I know:

$\mathbf {Force}$: is an interaction between an object and it's surrounding which causes the object to change it's momentum while the interaction is happening.

Now for gravitational and electromagnetic force I know about their classical model and, as far as I know, there they just are cause change in momentum of the object though one acts through charge and other acts through mass. But for weak nuclear force there is something more to it, it causes the particles on which it acts to change it's properties (like proton turning into neutron and vice versa) which is more than just a change in momentum.

So my questions is:

• Is there any modification to the definition of force to account for these?

Answer 1

Actually, most physicists agree with me about this, the term "force" is not well defined in strong and weak nuclear forces.

Really we have four interactions, and of those four, the EM and gravity interactions produce the classic EM force and gravitational force at low energies/large distances.

But the weak and strong interactions have no equivalent classical force. So to talk about the weak and strong force is really a misnomer. All physicists know that they aren't really forces in the sense that we can write them as $F(r)$ for some distance $r$.

When we talk about weak and strong interactions, what we are really doing is calculating scattering probabilities. And that includes the probability that new particles will be created during the scattering, e.g. like new particles are created at the LHC.