First of all, playing farther is not because the ball is faster. For a simple example, even amateur badminton players often hit the ball out of bounds in the backcourt, while professional players in the national team rarely go out of bounds. Professional players must be faster than amateurs. Theoretically, the air resistance is actually proportional to the ball speed. Assuming that the final speed of the ball becomes 0 (just assuming that it is not 0), the high-speed model is equivalent to making the ball speed finally 0, the initial speed is large and the acceleration is small (deceleration is large), while the low-speed model is equivalent to making the ball speed finally 0, the initial speed is small and the acceleration is large (deceleration is small), and the calculated moving distance is actually similar.

The hardness of the middle rod is more related to borrowing power. Soft middle pole is easy to borrow, hard middle pole is not easy to borrow. Because the borrowing force is beyond the player's control, the side effect of easy borrowing is that the uncontrollable factors of landing are greater, and it is more accurate to control landing if it is difficult to borrow. This is also the reason why "high-pound hard" is more popular with male professional players.

Finally, to answer your question, the hardness of the middle stroke is not directly related to the ball speed, but the ball speed is related to the instantaneous force you actually transmit to the ball. Some people may seem to be working hard all over, but they don't pass it on to the ball. That's why it's easy for people who can exert their strength to watch the ball, and people who can't exert their strength can't play well.

I hope I can help you.