Dinks
The art of dinking requires precise placement of the ball at low speeds. The ball can't be traveling too high lest the return will be smashed back. Too low or too slow and the ball is in the net. For dinks directly across the net the ball must be hit at an upward angle (30 to 40 degrees) at a speed of around 13 mph.
In the video it can be seen that for dinks directly across the net the distance traveled is 12 feet taking 0.9 seconds at a horizontal speed of 10 mph.(the horizontal component of a 13 mph dink directed at a 35 degree is about 10 mph) For cross court dinks the distance traveled is about 18 feet with an elapsed time around 0.9 seconds for an average speed of 15 mph.
The blue line on the graph shows the ideal dink. The ball is contacted 1.5 feet above the kitchen line with a velocity of 14 mph at an angle of 37 degrees. The ball clears the net by 6 inches and lands 1 foot inside the opponent's kitchen line. The orange line shows a problematic dink. The ball is contacted 1.5 feet above the baseline with a velocity of 17 mph at the same angle of 37 degrees. The ball pass above the net by 1.5 feet and is 3 feet above the ground when it reaches the opponent's kitchen line. It's a pop-up caused by hitting the ball at 17 mph rather than 14 mph.
The pros can be seen using a stiff wrist while pivoting the paddle around the shoulder. Pivoting around the shoulder would be inappropriate during a fire fight as more mass (the arm) means slower positioning, but that's not a problem when dinking. The advantage to a shoulder swing is the reduction in sensitivity to off-center hits. The picture shows the increased paddle velocity to a 2 inch off-center hit. When swinging from the wrist the paddle velocity increases from 14 to 17.5 mph if the contact point moves 2" down (8" from the pivot point to 10"). When swinging from the shoulder the velocity only increases from 14 to 15 mph (30" from the pivot point to 32") due to a mishit and a pop-up is avoided.
