|
Biomechanical
Principles to be Investigated:
Coeficient of elasticity
Purpose
This is a good lab for bringing in some direct applications of
physics. Energy conservation
is important here. The
concept of elasticity is related to the ball’s spring like ability to
convert kinetic energy to potential energy and back to kinetic energy.
The kinetic energies before and after the ball hits the surface are
related by energy conservation to the drop and bounce heights, so you are
in effect using energy conservation to determine the balls elasticity.
Each sport utilizes its own special type of equipment and playing
surface. How easy or
difficult it will be to throw, catch, bat, kick or strike a particular
game ball with the hand or racquet will depend on a) composition of the
ball, b) temperature of the ball, c) composition of the surface it
contacts and d) relative speed of both the game ball and the hand or
implement. Why? This lab will
investigate the coefficient of elasticity for a variety of game balls:
e =
bounce height
drop height
Rationale
The vast majority of lever segments of the human body favor the
development of speed and distance (i.e., third class lever system) over
the development of force production (i.e., second class lever system).
Thus, the ability to move one’s body quickly or to quickly throw
or kick an object a considerable distance requires tremendous internal
force production by the athlete. Two-thirds
to three-fourths of our skeletal musculature is arranged in a pennate
variation in order to maximize force production by distributing a large
number of muscle fibers within a given cross-sectional area.
But, despite the most advantageous pennate arrangement of muscle
fibers, force production is finite (i.e., per sarcomere : 22 - 28 N/cm2).
The evolution of sports equipment has always been guided by a combination
of physical attributes and limitations of the athlete. The use of lighter
materials with greater elastic properties, more shock absorbing materials,
more weather-resistant materials, and materials with lower air/fluid drag
coefficients have substantially improved athletic performances over the
past decade.
Athletic
success requires individual optimization of physical condition; selection
of the most effective sports equipment for individual somatotype, position
and ability level and participation in a sport which depends upon the
innate athletic ability of the individual.
Coaches and athletes should guard against substituting the larger
rewards gained from rigorous physical conditioning and long hours of skill
and agility training with the more limited rewards gained from advances in
sports equipment design.
References
Brooks, G.A., Fahey, T.D., & White, T.P. (1996).
Exercise Physiology: Human
Bioenergics and Its Applications (2nd ed.).
Mountain View, CA: Mayfielf
Publishing Co.
Kreighbaum, E. & Barthels, K.M. (1996).
Biomechanics (4th ed.).
Boston:
Allyn
and Bacon |
