Sorry for posting what may be an obvious question but we just learning about friction at school and my teacher couldn't explain well enough to me and I would appreciate your inputs.
Consider the following 3 cases:
1) A load of mass $m_2$ lies on a surface. The coefficient of friction between the load and the ground is $\mu$. You need to exert a force $F=\mu\cdot m_2\cdot g$ to pull the load, right?
2) A driver, e.g. locomotive of mass $m_1$ sits on the same surface and has the same coefficient of friction $\mu$ to it. The maximum force that this can exert is $\mu\cdot m_1\cdot g$, right?
3) Now, how can the locomotive pull the load at all? After all, it can just about pull itself? Now, I know that locomotives are able to pull their loads without issues. I mean, I am not getting some important concept here. Does the maximum traction that a locomotive can achieve increase if we hang a large load at it's back? That seems counterintuitive to me.
I would appreciate your help in understanding this. And thanks for your patience with a physics newbie.