No, there is an answer. That is, it is possible to provide motivation for Newton's laws. See, for example, the first chapter of V I Arnold's, Mathematical Methods of Classical Mechanics. The first step would be to argue for Galilean invariance. We don't know why nature has Galilean symmetry, and in fact, it doesn't. At least only approximately. Never the less, it is very clear why would WE would make such an assumption, as anyone who has ever been on a train can see (and as, Galileo argued originally, a ship at sea). There was a thread here, discussing how Newton came up with his laws.Well, and what's the answer?? There is no answer. We don't know why Newton's laws hold. We don't know why math is so suitable to describe the physical world. We introduce those laws because they seem to describe nature and because they make quantitative predictions. We don't know why they do and we can't ever explain why.
The OP has every right being upset. But that doesn't mean that he'll get a good answer to his question.
And that is one answer to the OP's question. DON'T deal with teachers who won't explain the concepts. Find a book or other source that does or come up with your own explanations.
And it doesn't end there. One may give enlightening and intuitive derivations, or one may obfuscate things with gruesome and unenlightening calculations, providing no physical intuition. A wise student will simply REFUSE to take this kind of crap, and will go and read someone who conveys some understanding, rather than incomprehensible, unmotivated nonsense.
There is just no excuse for the way some people are teaching.
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