A real physicist! PLEASE!

Discussion in 'Racquets' started by wolfpackfive, Aug 23, 2005.

  1. wolfpackfive

    wolfpackfive New User

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    From a real physicist (not a tennis player wanna be physicist), when hitting a ball with a racquet, is it Momentum (M=mv), Force (F=ma), or Energy (E=mv^2), that is at play?
     
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  2. Michelangelo

    Michelangelo Professional

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    First, the energy you mentioned should be kinetic energy, which is (mv^2)/2 (you miss the "1/2"). Secondly, all three things play since they involve mass and velocity (acceleration is the change of velocity). They're just the different faces of the same fact.
     
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  3. TW Staff

    TW Staff Administrator

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  4. TennisD

    TennisD Semi-Pro

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    Like someone has probably said already, you want to be thinking more of Kinetic energy rather than just energy in general...
     
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  5. AAAA

    AAAA Hall of Fame

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    Any moving object with mass will have speed, velocity, acceleration, momentum, kinetic energy and force and maybe a few other properties for a moving object with mass.
     
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  6. tennisee

    tennisee Rookie

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    I have a degree in mathematical physics - all three, force, momentum and kinetic energy are in play, but I think Chris from TW's suggestion of getting a book if you are interested is a good idea, as any meaningful discussion of the physics of tennis is way beyond a message board. I'd even be cautious with the book, as any modelling of a real-life situation such as tennis into a physics problem needs a number of assumptions and simplifications to be made, and these will only be valid up to a point. General principles are a good starting point, but over-simplification is a good way to come up with quick results that are wrong!

    But now that I'm started I may as well ignore my own advice...

    When a racquet strikes a ball it applies a force to that ball wich will change the ball's momentum. We can speak of the force applied as the rate of change of momentum, and the total momentum change as impusle. But we have linear and rotational momenta, and as well as a lnear force the racquet will typically also apply a torque that changes the angular momentum of the ball (changes its spin).

    It is also true that the racquet transfers kinetic enery to the ball, but much kinetic energy is lost in impact, mostly though deforming the ball, less through losses in strings and racquet. Also when hitting, translational kinetic energy of the racquet may be converted to rotational kinetic energy energy - spin again.
     
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  7. Waimea_Boy

    Waimea_Boy Semi-Pro

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    Don't forget about how the grip/wrist/arm affect the equation. A lot of force is absorbed/dissipated by your body and not tranferred to the ball.
     
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  8. harryz

    harryz Semi-Pro

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    Hey there, Wolfpackfive-

    Did you end up replacing your Black Max(s)? I used to play with them and am going to try them again. Would like to learn about your experiences with string/tension etc... could you email me (harryzweben@yahoo.com)? I'm having some trouble finding specs and info on the frame on line.

    Thanks!

    Harry Z
     
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  9. Vantage231511

    Vantage231511 Rookie

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    Dr. Brody's book is an excellent tretise on physics as it relates to tennis. For those who don't know, Dr. Brody is a professor emeritus at U of Penn, and has been at the forefront of the field since the late 1970's.

    He's also not a bad player...
     
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