I have Marion-Thornton 4th ed. around here somewhere. It is an older book and presents some material differently than we are used to in more modern books (for instance they even use the old imaginary time method when discussing some things in special relativity, which I personally dislike). However I agree with DanielSank, different pedagogy does not equal "nonsense".
Newton's laws are presented slightly differently by different books. For instance, it can be argued Newton meant his second law to be $F=dp/dt$ (although he didn't write it in this modern notation), although many books present it as $F=ma$. Some people go even further and try to extract a modern meaning, as I've seen some people say Newton's third law is the conservation of momentum. This may be pedagogically useful, but not historically accurate. It is worth reminding that some debate over the exact statements translated to modern language is understandable. Even though Newton invented calculus, some concepts in mechanics still took long after Newton to come into their modern understanding, such as the concept of kinetic energy was put in its modern form much later.
Thus to answer this question requires agreeing on a statement for Newton's third law. I don't have Marion-Thornton handy, so using wikipedia
When one body exerts a force on a second body, the second body simultaneously exerts a force equal in magnitude and opposite in direction on the first body.
The force between two particles in electromagnetism can violate this. For a concrete example consider a positive charged particle A pulled along the x axis at a constant velocity in the positive direction, and another positive charged particle B pulled along the y axis at a constant velocity in the positive direction. If it is arranged such that when A is at (0,0), B is at (0,1), then we can calculate the fields and find:
- the electric forces on the particles will be in opposing directions
- the magnetic force on A is zero
- the magnetic force on B is in the -x direction
Does this mean momentum is not conserved here? No.
If we include the person or device pulling these charges along as part of the system (so there are no external forces), then we should expect the momentum of the system to be conserved.
Where is the missing momentum then? It is in the fields!
I constructed this scenario specially to also help break a bad habit of some descriptions of this phenomena. Because the charges are moving at a constant velocity, there is no radiation. We don't need radiation to provide a force back on the partices or something to solve this. Momentum can be stored in the fields themselves. (While not shown in this example, even static fields can have non-zero momentum.)
The depth of the crater will depend primarily on three things:
- The height the marble is dropped from.
- The diameter of the marble.
- The mass of the marble.
To investigate Newton's 2nd law, you are going to have to keep 1. and 2. constant. That means finding marbles of different mass but the same size -- not easy. Assuming the size of the marble is fixed, then it is ok to assume a constant force from the flour. I am not sure what they are trying to suggest with the crater width -- don't worry about it.
Check out this video by Bruce Yeany on Newton's 2nd and 3rd law. His YouTube channel is very good, so you might want to come back to it sometime for future experiments and demonstrations.
Best Answer
Kinetic theory of gases is basically a pure classical theory of a system of non-interacting particles. In such a case, the collision of the particles with each other (which can be assumed to be elastic for very good approximation), and that will the container walls (giving rise to pressure) can be explained well using Newton's laws of motion. I will tell you about why this is not the case always.
When it comes to interacting particles like the electron gas, the kinetic theory fails. This you can find anywhere in books on solid state physics or condensed matter physics (about the failure of Drude model which used kinetic theory to the electron gas to explain electrical conduction). In such a case, one needs sophisticated tools like quantum mechanics to deal with interaction between the electrons. Also, as indicated in one of the comments, when the particles are in relativistic motion, simple mechanics cannot get into the details.
If you can negotiate with the above details, then kinetic theory is affordable to a very good extend.