Tip of the Week
Proper Forehand Technique - Circling and From Side.
The Height of a High-Toss Serve
The question that has plagued the world for many centuries is just how high you should toss a high-toss serve. After all, the higher you toss it, the faster it'll be traveling when you contact it, giving you more spin, right?
Actually, not really. Due to air resistance, any falling object in an atmosphere has a terminal velocity, but it varies based on its mass, cross-sectional area, drag co-efficient, air density, and gravity. For example, a little Googling tells us that a human body reaches terminal velocity in around 12 seconds - about 200 mph if falling feet- or head-first, about 125 mph if falling stomach- or back-first, with arms and legs spread out to maximize air resistance.
But how about a ping-pong ball? I found this online Terminal Velocity Calculator. For a ping-pong ball, the mass is 2.7 grams. The cross-section area is easy to calculate - it's the area of a circle with the diameter of a ping-pong ball, 40mm. Since A=Πr^2, and with radius 20mm, the cross-section area is about 1256.6 m^2. Some Googling found that the drag co-efficient for a sphere is about 0.5. Plugging these in, and using Earth's gravity and air density at sea level, we find that the terminal velocity of a ping-pong ball is about 18.55 mph.
But this doesn't tell us how high we have to throw the ball to get this maximum velocity. So I turned to my brother, Dr. Steven Hodges, a physicist and non-TT player (but great sailor!). He created this Excel file that does it for us.