Physics of Sports - Football and Tennis
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The document discusses the physics of football flight, highlighting factors such as weight, spin, and drag that influence trajectory. It explains the concepts of drag force, mentioning that a rougher ball performs better due to lower drag coefficients. Additionally, it covers the physics of racquetball, emphasizing the importance of hitting balls at the sweet spot for optimal performance.
Physics of Sports - Football and Tennis
- 2. Flight of a Football
- 3. • Round! And remain round! • Bouncy But not too much! • Water Proof • Swift Through the Air …Aaaand here comes the physics!
- 4. • Weight Acts downwards always Depends on how heavy the ball is • Magnus Force The direction depends on the motion of ball Depends on the spin on the ball Force is perpendicular to both spin and velocity Simple application of Bernoulli’s principle Higher Pressure Lower Pressure
- 5. • Question: Is it always true that the harder you kick the ball, the faster it goes? NO! • A new force enters the scene: the Drag Force! • Rule of thumb: The greater the turbulence, the greater drag force! • Drag Force is proportional to square of velocity. Faster the ball, greater the drag • Surprise! Drag suddenly decreases as the separation points coincide! (Image courtesy: Ken Bray article – A Fly Walks Around A Football)
- 6. A Rougher Ball is better than a Smooth One • Drag Coefficient = Measure of how much drag there is • Drag Coefficient falls sooner for a rougher ball than a smooth one • Drag Crisis: The fall is rapid! Which is a better football? A Smooth One or a Rough One? The rougher ball moves more smoothly than a smooth one!! Drag crisis (Graph courtesy: A Fly Walks Around A Football and Journal fo Fluid Mechanics)
- 7. Taking a free-kick = Aiming for a letterbox slit! • Weight, spin and drag affect ball trajectory • A free kick is not as easy as it seems! • Smooth is not always desirable
- 10. • Rigidity of the stem and flexibility of the head increased • Increase in the area of the head • Greater adjustability of the tension in the strings Wooden Aluminium Graphite
- 11. Dead Spot More bounce Sweet Spot Centre of mass Grip
- 12. Impact! Translation Rotation Final movement= + = If the ball is hit just right, there will be no impact on the grip Standard Physics: Every movement can be broken down to a translation and a rotation Vcm = V Vb = ω b Sweet spot:Vcm = VbBam!
- 13. • The racquet also vibrates! Impact Vibration • Third type of motion • Gives rise to two sweet spots • Can’t have both
- 14. Making the case for the central sweet spot even better! Hit the ball right from the middle of the racquet! Hold racquet at the proper grip position
- 16. Sources: http://sport.maths.org/content/ Articles on football flight by Ken Bray Physics of racket-ball interaction – by H.Brody, University of Pennsylvania Sweet spots of rackets – Hesston College article Big Thanks to my friends – too many to name and they know! Thanks to Arnab Sir and Kulkarni Sir
Editor's Notes
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