I Is calling fictitious forces "not real" just about terminology?

[Herman Trivilino]

My point is that most things in life involve considering cause and effect. Why bend over backwards to avoid this in the case of of N3?

The only bending over backwards is when uttering the phrase "action-reaction" instead of "Third-Law pair of forces". The former is a translation of a 17th century text. Who in the modern era uses "action" to refer to a force?

There is no reason to avoid cause and effect just because it's not strictly necessary.

There's no cause and effect here! That's the whole point.

These things will resolve themselves during the analysis.

Research shows otherwise. Students who are capable of solving chapter-end and test problems are overwhelming unable to answer questions involving the concepts of the Third Law. In other words, many students after successfully completing a course will be left with severe misconceptions. I've seen it when interviewing teaching applicants with a Ph.D. in physics.

One example of a misconception: If for every force there's a equal-but-opposite force how can there ever be a nonzero net force?

 

[Herman Trivilino]

I wonder whether that 'author' is in fact the product of a bit of AI composition.

Well, the first edition of the book where I took the "composition" from was published in 1990. I've got a later copy of it on my bookshelf. I've attended presentations by the author and spoken to him personally.

Edit: Sorry. I just realized I'd forgotten to state his name. Arnold B.Arons. University of Washington for many years. He's deceased.

 

[PeroK]

Arnold B.Arons. University of Washington for many years. He's deceased.

And who are we to argue with the late Arnold B Arons?

 

[PeroK]

Research shows otherwise. Students who are capable of solving chapter-end and test problems are overwhelming unable to answer questions involving the concepts of the Third Law. In other words, many students after successfully completing a course will be left with severe misconceptions. I've seen it when interviewing teaching applicants with a Ph.D. in physics.

One example of a misconception: If for every force there's a equal-but-opposite force how can there ever be a nonzero net force?

Now we have reached the nub of the matter. Unless we use your preferred terminolgy and look at physics your preferred way, and share your idiosyncracies, then we don't understand it at all and have the most basic misconceptions!

 

[sophiecentaur]

Research shows otherwise.

It's not a matter of "research". it's a matter of seeing what happens every time you analyse a system of forces. You can assign any direction to the force vectors you choose and their signs and directions will fall out of the calculation. That's what I was meaning.

 

[Herman Trivilino]

Now we have reached the nub of the matter. Unless we use your preferred terminolgy and look at physics your preferred way, and share your idiosyncracies, then we don't understand it at all and have the most basic misconceptions!

Not at all. I'm offering an opinion, not a mandate.

I didn't mean to imply that all students are left with these misconceptions, or that my suggested way is better than another. Just to point out that the phrase "action-reaction" has its problems.

 

[Herman Trivilino]

And who are we to argue with the late Arnold B Arons?

We're here to discuss different opinions, not to argue from authority. I apologize if I came off as doing the latter.

 

[A.T.]

There is no reason to avoid cause and effect just because it's not strictly necessary.

There is lots of reasons. Beyond Occam's razor, it leads to misguided notions, which stand in the way of proper analysis. See the examples in post #55.

it's the equivalent of choosing arrow directions on a free body diagram.

No, it's not equivalent:
- Sign conventions / arrow direction definitions are required to do the math.
- The action / reaction assignment in N3 is irrelevant for the math.

The flow of causality intuitively follows the flow of energy so where is the problem?

Explained by @jbriggs444 in post #60.

These things will resolve themselves during the analysis.

How does action/reaction in N3 resolve itself during the analysis? It doesn't even enter a correctly done quantitative analysis. At most it just confuses and prevents or delays a correct analysis.

 

[PeroK]

There is lots of reasons. Beyond Occam's razor, it leads to misguided notions, which stand in the way of proper analysis. See the examples in post #55.

Can you prove that the arguments about DDWFTTW are between those who understand N3 as you do and those who do not understand it?

It sounds like a bogus argument to me.

 

[A.T.]

It sounds like a bogus argument to me.

Then stick to the Occam's razor reason.

 

[Herman Trivilino]

It's only when the rocket engine has been lit that any acceleration can happen. The reverse description "If we see the space ship accelerate then there has to be a force acting" has to involve an 'if'. Doesn't that imply some directionality?

I guess I don't get it. I can write equivalent versions of your two phrases, placing "if" in the other one ...

“If the rocketship is accelerating then the rocket engine is lit”

“There has to be a force acting on the space ship to make it accelerate”