1. The Forehand: Slice vs. Topspin
Pranav Reddy

2. Background
The 3 basic strokes: -topspin- offense or defense -slice: defensive -flat- offensive
I will concentrate on the first two

3. Grips

4. Professional Topspin shot

5. Professional Slice

6. 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 power

7. 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 maximus

8. 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)
hand

9. Tennis Injuries
But I will focus on more common injuries…

10. Overuse Injuries Tennis elbow Bursitis of elbow
Rotator cuff tendonitis
Shoulder tendinitis
Frozen shoulder
Wrist tendonitis

11. Acute Injuries Wrist sprain Shoulder separation Torn rotator cuff
Therefore proper form and training needed

12. Experiment Compare the topspin and the slice shots
Differences in racquet contact
Differences in spin
Differences in translational kinetic energy
Differences in rotational KE

13. Contact and spin slice 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 videos

14. Differences in KE KE=1/2(mv^2) KE is transferred from racquet to ball
Rotational KE(1/2 Iw^2)
See results next slide

15. 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/s
total initial velocity: 2.24 m/s
Initial KE= 0.5(0.058)(2.24^2)= Joules
X-velocity after: 20.2 m/s
Y-velocity after: 10.4 m/s
Total velocity after : 22.72m/s
KE after: 0.5(0.058)(22.72^2)=14.97 Joules

16. Topspin: KE Rotational
assume ball is coming at racquet with no spin; rotational KE is not a factor before impact
Rotational KE after
1 revolution of ball took 4 frames
Camera shot in 240 frames per sec
Time for one full rev (T)= 4/240= sec
Angular velocity(w)= 2pi/T= rad/sec
KE=0.5(I)(w^2)=0.5(3.96e-5)(376.3)= J
Note: the moment of inertia of tennis ball(hollow sphere) is equal to 2/3(m)(r^2)
Now lets compare with slice….

17. Slice: Translational KE
Initial X- velocity of ball: 1.85 m/s
Initial Y- velocity of ball: 1.37 m/s
total initial velocity: 2.30 m/s
Initial KE= 0.5(0.058)(2.30^2)= Joules
X-velocity after: 14.7 m/s
Y-velocity after: 5.1 m/s
Total velocity after : 15.56m/s
KE after: 0.5(0.058)(15.56^2)=7.02 Joules

18. Slice: KE rotational
Again, assume ball is coming at racquet with no spin; rotational KE is not a factor before impact
Rotational KE after
1 revolution of ball took 7 frames
Camera shot in 240 frames per sec
Time for one full rev (T)= 7/240= 0.029sec
Angular velocity(w)= 2pi/T= rad/sec
KE=0.5(I)(w^2)=0.5(3.96e-5)(216.7)= J
Note: the moment of inertia of tennis ball(hollow sphere) is equal to 2/3(m)(r^2)

19. KE transfer
A total of 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 translational
Slice case: 99.94% of the ball’s KE after impact was translational

20. 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.

21. Further Investigation
-Many possibilities for future experiments
Elasticity of strings: certain types and tensions
The flat shot: quite powerful
two handed vs. one handed: different players have different styles

22. 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 rotation

23. References

24. Thank You