One of the first TT documents I came across was this one below. I got it off the ITTF website. I haven't been able to find it on the ITTF website for years now but I have many terabytes of stored data.
Notice the second short paragraph on the first page. It talks about the mysticism of TT and how hard it is to talk about reality. This was very true. It was hard to explain reality to hard headed idiots on mytt.
I posted a link to this document many times and it was ignored. I would make fun of the people on mytt by asking them to define throw angle. No one could and people couldn't even agree on whether a rubber had high or low throw angle. It was fun trolling them. Yes, I am bad by making fun of the ignorance and pointing it out. On mytt they preferred to burn, ban me , the heretic rather than simply try to understand .
The document talks about the normal and tangential coefficient of restitution and how it changes with impact speed. The basics of this document are still valid but now the ball is a little bigger and harder than it was before. Supposedly the rubbers are a little faster too but the basics still apply.
https://deltamotion.com/peter/TableTennis/199408014 - Tiefenbacher - Impact.pdf
TT players tend to make up terms for things they don't understand. Throw angle is one of them. The last year I have seen more people talk about spin to speed but both can be related to the normal and tangential coefficient of restitution. It is best to use the ratio of the tangential coefficient of restitution to the normal coefficient of restitution instead of throw angle. Tests should not include humans as they are not calibrated.
Read the document. I can explain.
Dwell time is harder to explain and has many more myths and misconceptions. Going way back there was a forum member on mytt that called himself Anton Chigurh ( from the movie ). His thread was called "obscure question", It was about dwell time. Again, people couldn't define dwell time and that made talking to the hard headed idiots difficult. The problem is that many were trying to call dwell time as what they felt. I was trying to explain it is actual contact time. Because there were two definitions there was a lot of disagreement, hate, and discontent. I would make fun of the "touchy feelly" people. That included Baal at first. Baal did say that by the time the nerve pulses reached the brain the ball was long gone.
I admit, I had lots of fun trolling the "touchy feely" people. Eventually Baal came around and did that he called his "napkin" calculations. It was crude but it was in the ball park. Baal was the ONLY person that even tried to estimate the true contact time. I had a lot of contempt for all those so called PhDs that did nothing but hide. The problem with Baal's calculation is that it assumed a linear deceleration until the ball stopped and a linear acceleration till the ball left the paddle. This isn't what happens. When the ball first makes contact with the rubber the rubber provides no resistance. Resistance increases as the ball penetrates the rubber. As resistance increases the ball decelerates at faster rates until all the kinetic energy is transformed into potential energy in the compressed rubber, ball and blade. Now comes the tricky part. The sponge, foam rubber has internal resistances or damping. Also, now that the sponge is compressed. The energy must now not only push the ball, it must accelerate the sponge fast enough to stay in contact with the ball. Simulating the impact part is easy. Simulating the rebound is not. It takes some assumptions.
However, what is interesting is what what the peak force can be on the paddle during impact. Does anyone care to estimate?
Another myth is accelerating through the ball. If the paddle is still accelerating then it isn't at maximum speed at contact.
If the paddle is not at maximum speed at contact and accelerating past contact will only make recover time longer.
Dwell time can be infinite. Normally is is quite short.
On Anton's "obscure question" is posted a link to a video made by Tacshow123. I may have the spelling wrong. tacshow123 catches the ball on his paddle. In this case the dwell time is infinite. So what conditions are necessary to extend dwell time? I was banned on this forum when trying to show the answer. This forum never get an answer now, unless.
Here is another questions. Let's assume you brush the ball and the ball deforms or stretches the rubber 0.1mm. If the dwell time is 1 ms then let's assume it takes 0.5 ms for the rubber to be stretched and 0.5 ms to rebound, then the rubber will cause a tangential motion of 0.1mm in 0.5 ms to help spin the ball. So what of the dwell time is shorter by half. Then the rubber will rebound .1mm in 0.25ms which is twice as fast for even more spin. So is longer contact/dwell time better?
What I have found disturbing over the years is that even those with PhDs hide.
Eventually, the engineers will find a way to make a robot that can move with the grace and speed of a human. The math and physics already exists to beat the best in the world. The limitation is the mechanics.