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View Full Version : Re: PP126: F-V PARADOX

Tony Blazevich
10-21-1999, 03:54 PM
Dear list members,

Thanks to Mel for the Paradox. For what its worth, since all the balls are
of the same size, air resistance is identical for each ball, the effect of
this resitance isn't. Air resistance is a negative force. This negative
force counteracts the momentum of a ball to slow it down. The more a ball
slows down in flight, the shorter is the distance it travels.

Momentum is a product of Force and Velocity. However, for human muscle,
this relationship is not linear. We cannot throw a ball of half the weight
twice as far (even in a vacuum, we can see this if we try to throw very
heavy weights, which can only be thrown at low velocities where air
resistance is negligible). If we could, we'd be able to throw something
that was about 0.0000000001 kg at an infinite velocity, and therefore an
infinite distance. Thus, very light balls have less momentum since their
velocity isn't increased as much as its weight has decreased compared to
slightly heavier balls, even if we exert a maximal effort. Since the
lighter balls have less momentum, the opposing force required to slow the
ball is less. If all balls have the same surface area, and therefore wind
resistance, the force of air resistance will have a greater effect on the
velocity of lighter balls.

Therfore, the ball that we throw optimally have a weight that we, as
individuals with different force-velocity characteristics of our muscles,
can impart the greatest momentum on, not just throw at the highest
velocity. That weight will be neither a very heavy, or very light, ball.

Tony.

************************************************** ****************
Anthony (Tony) Blazevich
School of Exercise Science and Sport Management
Southern Cross University
Lismore NSW Australia, 2480

Email: ablaze20@scu.edu.au
Phone: +61 2 6620 3231
Fax: +61 2 6620 3880
Mobile: 0416 200 674 (Australia only)

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