Putting aside the physiology and biomechanics.. I reckon the physics experts that'd have really good understanding of force power and momentum and kinetic energy, including even details about how long the projectile is in contact with the strings, would be the the scientific advisors behind the machines that state whether a projectile is in the court or out of the court. When those computers show a video of a tennis ball landing, that has people staring mistakenly thinking they are looking at the gospel truth, it's actually just a video that was constructed by predicting where the ball would land, made long before it landed. Whatever expertise they have would have us covered for answers related to the physics! I wonder if it's a particular branch of physics?
For tennis, the dwell time (how long the ball is in contact with the stringbed) is typically 4 or 5 milliseconds. This dwell time is pretty much independent of swing speed but is affected by string tension and, to a lesser extent, other physical factors of the racket & ball. The typical dwell time for badminton contact may be a bit different but is probably still on the order of a few milliseconds.
There is a considerable amount of info (studies, books & articles) on sports physics for golf and tennis. No doubt that there are also some sources, in English, for badminton physics. I will try to dig up a couple of sources to get you started if you are interested
Even tho Hawkeye typically employs 6 to 10 high speed cameras and some pretty sophisticated algorithms for line calls, the system will very rarely, if ever, pick up the actual bounce (court contact). That contact is probably only 3 ms or so and will usually not be seen by their high-speed cameras. (Ultra-high speed cameras, that can catch the actual bounce, are much too expensive to be practical for a line-calling system such as this).
So, what we actually get from the Hawkeye system is calculated (extrapolated) trajectories and contact based on the information gleaned from several high speed cameras. A knowledge of physics along with some sophisticated software algorithms is utilized to present those graphic representations of trajectories and court contacts.
The contacts we are shown are supposed to be within a few mm, on average, from the actual contact. So a graphic representation that shows the ball or shuttle to be IN or OUT by 1 mm (or even 3 mm) can very well be incorrect. The challenge might be even greater for tennis than for badminton since wind is a significant factor. There are also Magnus effect factors for various types of spins employed in tennis. Magnus effect has a pronounced effect on trajectory. Badminton primarily employees only one type of spin. Even tho there is considerable air drag, there is little or no Magnus effect TMK.
