Physik im Sportbmbf德国physik IM运动

1、Tennis and PhysicsThe and his featuresnDiameter: 6,35 - 6,67cmn Wheight: 56,70 - 58,47gn Jumphight: 1,346 - 1,473m on hard floor from 2,54m height of fall (20 C temperature)Coefficient of impact eThe conservation of energy is effective:ghvmvmghEEKINPOT22211vve Definition of the coefficient of impact

2、 e:1111*2*2hhhghgeIt follows:Coefficient of impact e8 , 054, 2473, 17 , 054, 2346, 1MAXMINeeIt is effective for the :Different coefficients of impactrubber ball: 0,9golf ball: 0,84baseball: 0,5Experiments of Balldeformitydouble load = double deformityHookes lawdouble force double way of the feather!

3、Hookes law: F = k *xPeriod of oscillation and contact time of the Period of oscillation T = 10 - 12mscontact time T/2 = 5 - 6ms Contact time of the racketThe 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 os

4、cillation is available and doesnt 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 stringDifferent s

5、trings 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 yo

6、u can bang very hard and strong balls, because of the elasticity of the soft strings like a trampoline does. (John Mcnroe)Sweet SpotRotation of theBack-SpinTop-SpinDriveMagnus effectThe Magnus effect has his name of his inventor Gustaf Magnus!No spin of the ball causes that the airstream regularly s

7、treams over and under the ball.If you play the spin, the air molecules in the balls felt are carried away.This effectuates that the airstream speads up the ball.Lift or downward pressure!The Magnus effect in tennisThe Magnus effect is specially set in by playing the back and the topspin.First becaus

8、e 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 sensors2 kinds of playing tennisForehandServeForehandRota

9、tiontablePlayerRPM RangeAvg RPMSergi Bruguera2941-3751 rpm3331 rpmThomas Muster1500-3750 rpm2882 rpmMarcelo Rios1875-3750 rpm2647 rpmMark Philippoussis 2143-2727 rpm2546 rpmJim Courier938-3264 rpm2527 rpmMichael Chang1271-3192 rpm2334 rpmPete Sampras1000-3409 rpm1842 rpmAndre Agassi1154-3333 rpm1718

10、 rpmTodd Martin1154-2308 rpm1659 rpmTim Henman833-2000 rpm1288 rpmPetr Korda968-2500 rpm1333 rpmShot: Mens ForehandRotationtablePlayerRPM RangeAvg RPMVenus Williams1071-3488 rpm2154 rpmMary Pierce1667-2500 rpm1941 rpmArantxa Sanches1875-2000 rpm1916 rpmAnna Kournikova1154-2143 rpm1713 rpmJana Novotn

11、a1500-1875 rpm1673 rpmLindsay Davenport1271-3192 rpm1346 rpmMonica Seles790-1829 rpm1215 rpmMartina Hingis600-2143 rpm1147 rpmMary Jo Fernandez 417-1500 rpm1068 rpmShot: Womens ForehandWhat a tennis teacher has to know Principle of independence of the motion!Height of the net: s = 91cmdistance of th

12、e net-baseline: 12macceleration of gravity: 10m/s2What a tennis teacher has to knows=g/2 * t2 t2 = 2s/gt 0,43sv = s/t 28m/s 100km/hServeServeThe Speed of the Serve with the Help of the wrist-sensorWhat you have to know:arm+masse of the racket weighdestine a with the wrist-sensorcontact time = 5msmasse of the ball = 0,058kgBASBmtamvThe worldrecord of serving:13.4.2004 Andy Roddick150 mphRotationtableRot