Transcript Introduction to Program Evaluation

Kinematic and
Energetic Concepts
Dr. Suzan Ayers
Western Michigan University
(thanks to Amy Gyrkos)
Terms
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Kinematics: aspects of motion w/o consideration
of mass and force
Kinetics: effects of forces upon motions of
material bodies
Energetics: energy and its transformations
Motion: describes displacement, velocity and
acceleration of a body in space
– Displacement: Δ in body’s position between locations
– Velocity: rate of Δ in body’s displacement over time
– Acceleration: rate of Δ in body’s velocity over time
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Centrifugal: away from the center/axis
Centripetal: toward the center/axis
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Force: measure of the amount of effort applied
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– Internal force: applied by one part of body on
another part of the same body
– External force: applied by another object
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Moment of force: measure of the force needed
to rotate a body around a point
Equilibrium: all points of body have = velocity
– Static equilibrium: all points’ velocity/acceleration=0
Quadriceps force production
throughout the ROM
Scientific Units of Measure Highlights
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Force (F): newton (N), some kg
– 1kg=9.81N
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Work (w): distance + force; joule (J)
Velocity (v): km/h, m/min, m/s, °/s, rad/s
Power (P): watts (W) (force*distance)/time spent moving object
Energy (E): joule (J)
Boxes 2.1-2.4 (p. 25)
Table 2.4 (p. 26)
Newton’s Laws
I. Law of Inertia
– Every object in a state of uniform motion tends to
remain in that state of motion unless an external
force is applied to it.
object must overcome inertia for movement to occur
Formula:
___kg x 9.81 m/s2 = ___ (force must be > than this to move)
(Body wt in lbs / 2.2 = kg) i.e., 150#/2.2=68 kg
68 kg x 9.81 m/s2 = 667.1N required to move 68 kg
Factors influencing inertia: friction, air resistance
(e.g., base runner, skier)
II. Law of Acceleration
– Change of motion is proportionate to the force
impressed and is made in the direction of the
straight line in which that force is impressed.
Objects accelerate in the direction pushed
Formula:
F = ma
Mass (in kg) m, acceleration a, and applied force F
Directly proportional (push 3x harder=3x> acceleration)
Inversely proportional to mass (object that is 3x heavier
moves 1/3 slower; bowling ball vs. volleyball)
If force or time ↑, so does velocity (i.e., keeping contact w/
ball longer = > time)
Momentum
– Product of mass & velocity
– Changes as a function of mass/velocity Δs
Velocity Δ: shot putter who spins faster one time vs
another
 Mass Δ: swinging a heavier bat
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– Short stopping time requires ↑ force to Δ
momentum velocity
i.e., ‘giving’ when catching a ball or landing
 Key to injury prevention
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III. Law of Action-Reaction
– Every action has an = and opposite reaction
Energy and Power
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Kinetic energy: mechanical energy due to motion
(joule, J)
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Potential energy: mechanical energy by virtue of
height above ground (joule, J)
Elastic strain energy: stored energy in elastic
tissues of muscles and tendons
Power: rate of doing work
(aka, strength x speed)
(joule, J)
– Positive: concentric contractions produce energy
– Negative: eccentric contractions absorb energy
Points of Application
1) Which muscles most important in the vertical jump?
 Quadriceps and gluteals
 SO WHAT?!
2) Relative to metabolic energy consumption…
 The cost associated with quiet standing is ~30% higher than
resting (sitting/lying down)
 SO WHAT?!
3) Walking saves met energy by converting gravitational
potential energy into forward kinetic energy. Running
stores/re-uses elastic strain energy, but less efficiently than
pendulum-like walking mechanism.
 SO WHAT?!
 Running less efficient than walking, ergo > caloric cost