I have a masters degree in Mechanical Engineer.

What was your specialty in school? What are you doing now?

• Hook's Law - yeah, I didn't want to explain 'empirical law' or try to describe the stress-strain curve & the various stress states represented.
• Stress without strain isn't too hard to explain, point to a big bridge and explain the gaps in the roadway. "Thermal expansion", if constrained, leads to stress with no motion.
• Stain without stress is the opposite side of that coin. Those bridges actually move without any forces being applied to them, they expand as they get warmer.

But let's not get into all of that.

I agree, let's not bore anyone with mechanics. ;)