Pranav Reddy Background The 3 basic strokes topspin offense or defense slice defensive flat offensive I will concentrate on the first two Grips Professional Topspin shot http wwwyoutubecomwatchvpM0jYWfVFMwampfeaturerelated ID: 744980
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Slide1
The Forehand: Slice vs. Topspin
Pranav
ReddySlide2
Background
The 3 basic strokes:
-
topspin- offense or defense-slice: defensive-flat- offensive
I will concentrate on the first twoSlide3
GripsSlide4
Professional Topspin shot
http
://www.youtube.com/watch?v=pM0jYWfVFMw&feature=relatedSlide5
Professional Slice
http
://www.youtube.com/watch?v=wFcamvUEulQSlide6
Kinetic Chain
-Power in tennis is generated via muscles working together as a chain
-transfer of energy from one part of body to another
-the arm alone won’t generate enough powerSlide7
Kinetic Chain: Transfer of energy
Kinetic chain starts in lower body
Begins in feet: power is created as feet push off ground
Lower legs (calves)Upper legs (quadriceps and hamstrings)Gluteus maximusSlide8
Kinetic Chain: Transfer of Energy
Energy then transferred to hips( abductors and adductors) and core; used for rotation
Pectorals
Shoulder(deltoids)Upper arm (biceps)Forearm (brachialis) handSlide9
Tennis Injuries
But I will focus on more common injuries…Slide10
Overuse InjuriesTennis elbow
Bursitis of elbow
Rotator cuff tendonitis
Shoulder tendinitisFrozen shoulderWrist tendonitis Slide11
Acute Injuries
Wrist sprain
Shoulder separation
Torn rotator cuffTherefore proper form and training neededSlide12
Experiment
Compare the topspin and the slice shots
Differences in racquet contact
Differences in spin Differences in translational kinetic energyDifferences in rotational KESlide13
Contact and spinslice stroke: racquet head cuts under the ball
topspin: racquet face comes over the ball
This difference in contact leads to differences in KE
See my videosSlide14
Differences in KEKE=1/2(mv^2)
KE is transferred from racquet to ball
Rotational KE(1/2 Iw^2)
See results next slideSlide15
Topspin: Translational KE
Mass of tennis ball: 0.58 kg
Initial X- velocity of ball: 1.81 m/s
Initial Y- velocity of ball: 1.32 m/stotal initial velocity: 2.24 m/sInitial KE= 0.5(0.058)(2.24^2)=0.1455 JoulesX-velocity after: 20.2 m/sY-velocity after: 10.4 m/sTotal velocity after : 22.72m/sKE after: 0.5(0.058)(22.72^2)=14.97 JoulesSlide16
Topspin: KE Rotational
assume ball is coming at racquet with no spin; rotational KE is not a factor before impact
Rotational KE after1 revolution of ball took 4 framesCamera shot in 240 frames per secTime for one full rev (T)= 4/240= 0.0167 secAngular velocity(w)= 2pi/T= 376.3 rad/secKE=0.5(I)(w^2)=0.5(3.96e-5)(376.3)=0.0074 JNote: the moment of inertia of tennis ball(hollow sphere) is equal to 2/3(m)(r^2)Now lets compare with slice….Slide17
Slice: Translational KE
Initial
X- velocity of ball:
1.85 m/sInitial Y- velocity of ball: 1.37 m/stotal initial velocity: 2.30 m/sInitial KE= 0.5(0.058)(2.30^2)=0.1534 JoulesX-velocity after: 14.7 m/sY-velocity after:
5.1
m/s
Total velocity after :
15.56m/s
KE after: 0.5(0.058
)(15.56^2)=7.02
JoulesSlide18
Slice: KE rotational
Again, assume
ball is coming at racquet with no spin; rotational KE is not a factor before impact
Rotational KE after1 revolution of ball took 7 framesCamera shot in 240 frames per secTime for one full rev (T)= 7/240= 0.029secAngular velocity(w)= 2pi/T=
216.7
rad/sec
KE=0.5(I)(w^2)=0.5(3.96e-5
)(216.7)=0.0043
J
Note: the moment of inertia of tennis ball(hollow sphere) is equal to 2/3(m)(r^2)Slide19
KE transfer
A total of 14.83 Joules were transferred from racquet to ball in the topspin shot
Whereas only 6.87 Joules were transferred in the slice shot
Topspin case: 99.95% of ball’s KE after impact was translationalSlice case: 99.94% of the ball’s KE after impact was translationalSlide20
Conclusions
Regardless of the type of shot, the rotational KE of ball after impact is very little compared to the translational KE of the ball after impact. The ratios of rotational KE to translational KE after impact were essentially the same for both shots.
The type of shot certainly affects the amount of energy transferred from the racquet to the tennis ball.
The topspin shot had a greater rotational KE transfer compared to the slice. This is expected: the racquet comes over the ball faster in a topspin shot than it does in cutting underneath the ball in a slice shot. If the racquet cuts too fast under the ball in a slice, this will result in a drop shot rather than a normal slice.The topspin shot also had a greater transfer of translational KE. This is expected since the topspin is more of an offensive shot therefore it is hit with a greater velocity, while the slice is more of a defensive shot and therefore is expected to involve a smaller transfer of translational kinetic energy.Slide21
Further Investigation
-
Many possibilities for future experiments
Elasticity of strings: certain types and tensionsThe flat shot: quite powerfultwo handed vs. one handed: different players have different styles Slide22
Further Investigation
Why does forehand tend to be more powerful compared to backhand?
-uses deltoids and biceps rather than weaker muscles(triceps and anterior shoulder muscles)
-uses more hip due to open stance, therefore more rotationSlide23
References
http://
sportsmedicine.about.com/od/tennisinjuries/a/tennisinjuries.htm
http://www.livestrong.com/article/105577-muscles-body-used-tennis/
https://www.msu.edu/~jochmans/physicsoftennis.htmlSlide24
Thank You