ROD CROSS HOME PAGE

      

Why won't this metal tube "sing" when I hit it with a tennis ball? It does when I hit it with a golf ball.

Listen to a bell (recorded at the same volume and ball speed) hit with

(a) a golf ball       or      (b) a tennis ball

The bell might sound tinny if you use internal speakers. Try it anyway as a test of the bass response of your internal speakers. The fundamental frequency is 975 Hz. Internal speakers will not respond at all to the f < 200Hz racquet sounds included on the tennis page.

Brief CV

Born 1943. Lived in Berry, NSW until age 14 then moved to Forbes. B.Sc. Dip. Ed at Sydney University. PhD in plasma physics in 1968. From 1968 to 1996 I worked in the Plasma Physics Department at Sydney University, specialising in Alfven wave studies in the TORTUS tokamak. I retired in 2003 as an Honorary member of staff, to continue work on the physics of sport and forensic physics.

 

 

 SPORTS PHYSICS

                                    

(At 1000 f/s)                      (At 1000 f/s)    

         

                                           FOOTBALL

 

Superball 1000 f/s (note spin reversal)

TENNIS BALL at 3000 f/s  incident at 30 m/s on clay and on grass (copyright by ITF). Can be viewed with QuickTime or RealPlayer and is in H.264 compressed format. Note how clay sticks to the ball and is then spun off. The grass here was longer than normally seen at Wimbledon. Grass is a faster surface than clay, even when the grass is long. You can work out the bounce speed, spin and angle yourself from this film.

TENNIS STRINGS at 1000 frames/sec (using a 725 g boule incident at low speed)

COLLISIONS

BILLIARDS

 MORE TENNIS    and   FIVE WAYS TO WIN A POINT

BALL TRAJECTORIES

WOBBLE BOARDS & MUSICAL SAWS

FORENSIC PHYSICS

PUBLICATIONS  (and  TENNIS MAGAZINE ARTICLES)

Contact: cross@physics.usyd.edu.au     Ph: +61 2 9351 2545   or   +61 02 9351 2545