ROD CROSS HOME PAGE
A recent (2009) photo
evidence for murder (UNSW Press) NEW
BOOK (Oct 09)

Channel 10 Movie
Clip (QuickTime) from ÒA Model DaughterÓ 4 Nov 2009
Technical Tennis by Rod Cross and Crawford Lindsey

Available from www.racquettech.com, amazon.com etc (only $11 for priceless
information!)
Remember this:
ÒSex is good but tennis lasts longerÓ Freud, 1938.
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SPORTS PHYSICS
(At 1000 f/s) (At 1000 f/s)
Superball 1000
f/s (note spin reversal)
HOOP Bounce1, Bounce2, Bounce3 at 600
fps The hoop slides then grips
before bouncing, in the same but in a much more obvious manner than a ball. It
is also obvious, especially in bounce2, that the normal reaction force does not
act through the centre of mass and therefore exerts a strong torque on the
hoop, reducing the spin rate. The same effect occurs with spherical balls.
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 and BOUNCE
OF AN OVAL FOOTBALL
BILLIARDS
MORE TENNIS
and FIVE WAYS TO WIN A POINT and TENNIS
STATISTICS
BALL
TRAJECTORIES
WOBBLE BOARDS & MUSICAL SAWS
LISTEN TO A BELL (recorded at the same volume and
ball speed) hit with
Why are the sounds so different?
ItÕs the same fundamental reason that some bats and racquets have bigger sweet
spots than others. The amount of vibration depends on the ratio of impact
duration to the vibration period. 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.
This is a pretty picture of a golf
ball and an 8mm thick slice of a large superball sitting on a slab of polished
granite. The ball spins faster when it bounces off the superball slice since
the tangential coefficient of restitution is much larger. A golf ball that
spins faster will travel further. Click on photo to see a simplified
explanation of why the ball spins faster. The same effect occurs with tennis
strings.
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Some cases I have worked on with NSW Police and Coroner
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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.
PUBLICATIONS
(and TENNIS MAGAZINE
ARTICLES)