Transcript Physik im Sport

Tennis and Physics
The
and his features
Diameter: 6,35 - 6,67cm
 Wheight: 56,70 - 58,47g
 Jumphight: 1,346 - 1,473m
on hard floor from 2,54m height
of fall (20° C temperature)

Coefficient of impact e
The conservation of energy is effective: E POT  E KIN
m v2
m gh 
2
v  2 gh
2 * g * h1'

2 * g * h1
h1'
h1
It follows:
e
Definition of the coefficient of impact e:
v1'
e
v1
Coefficient of impact e
It is effective for the
eMIN
1,346

 0,7
2,54
eMAX
1,473

 0,8
2,54
:
Different coefficients of impact
rubber ball: 0,9
golf ball: 0,84
baseball: 0,5
Experiments of Balldeformity
double load =
double deformity
Hooke‘s law
double force  double way of the feather!!!!!
Hooke´s law:
F = k *x
Period of oscillation and contact
time of the
Period of oscillation T = 10 - 12ms
contact time T/2 = 5 - 6ms
Contact time of the racket
The contact time is approximately 15ms!
The time is too big to make a contribution for the
ball. That means that the racket ,,wastes“ energie!
The oscillation is available and doesn`t pass over
the ball, but loads the wrist and mainly the ellbow.
Tennisellbow!
Contact time of the string
The contact time is 5 ms and that is the same as that from the
ball!
Attention: „Vibrastop“ losses the oscillation of the string!
Contact time of the string
Different strings are a result of clamping different
weights of the strings in the racket. It is effective that
there are soft and hard strings.
The hard strings are very good for the controlled
Top-Spin-Game, but not for very fast and varied game.
(Thomas Muster)
The soft string is very difficult to play but you can
bang very hard and strong balls, because of the
elasticity of the soft strings like a trampoline does.
(John McÉnroe)
Sweet Spot
Rotation of the
Back-Spin
Top-Spin
Drive
Magnus effect
The Magnus effect has his name of his inventor
Gustaf Magnus!
No spin of the ball causes that the airstream regularly
streams over and under the ball.
If you play the spin, the air molecules in the ball‘s felt
are carried away.This effectuates that the airstream
speads up the ball.
Bernoulli-equation
Lift or
downward pressure!!
The Magnus effect in tennis
The Magnus effect is specially set in by
playing the back and the topspin.
First because the magnus effect changes the
trajectory of the ball!
To effectuate different effects at the time of
the impact of the ball in the field!
To change the interplay between the ball and
the racket because of the spin!
Reading with the help of the
sensors
2 kinds of playing tennis
Forehand
Serve
Forehand
Rotationtable
Shot: Men's Forehand
Player
RPM Range
Sergi Bruguera
Thomas Muster
Marcelo Rios
Mark Philippoussis
Jim Courier
Michael Chang
Pete Sampras
Andre Agassi
Todd Martin
Tim Henman
Petr Korda
2941-3751 rpm
1500-3750 rpm
1875-3750 rpm
2143-2727 rpm
938-3264 rpm
1271-3192 rpm
1000-3409 rpm
1154-3333 rpm
1154-2308 rpm
833-2000 rpm
968-2500 rpm
Avg RPM
3331 rpm
2882 rpm
2647 rpm
2546 rpm
2527 rpm
2334 rpm
1842 rpm
1718 rpm
1659 rpm
1288 rpm
1333 rpm
Rotationtable
Shot: Women's Forehand
Player
RPM Range
Venus Williams
Mary Pierce
Arantxa Sanches
Anna Kournikova
Jana Novotna
Lindsay Davenport
Monica Seles
Martina Hingis
Mary Jo Fernandez
1071-3488 rpm
1667-2500 rpm
1875-2000 rpm
1154-2143 rpm
1500-1875 rpm
1271-3192 rpm
790-1829 rpm
600-2143 rpm
417-1500 rpm
Avg RPM
2154 rpm
1941 rpm
1916 rpm
1713 rpm
1673 rpm
1346 rpm
1215 rpm
1147 rpm
1068 rpm
What a tennis teacher has to
know
Principle of independence of the motion!
Height of the net: s = 91cm
distance of the net-baseline: 12m
acceleration of gravity: 10m/s2
What a tennis teacher has to
know
s=g/2 * t2
t2 = 2s/g
t  0,43s
v = s/t  28m/s 100km/h
Serve
Serve
The Speed of the Serve with
the Help of the wrist-sensor
What you have to know:
arm+masse of the racket weigh
destine a with the wrist-sensor
contact time = 5ms
mS  A  a  t
vB 
mB
masse of the ball = 0,058kg
The worldrecord of serving:
13.4.2004
Andy Roddick
150 mph
Rotationtable
Rotationtable
We hope you have enjoyed
our presentation
A presentation from: Raphaela Böhm, Petra Fegerl, Evelin
Nagelmaier, Verena Weinberger
And we are grateful for the help of our teacher
MR. BINDER