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Basic Concepts Related To
Kinetics
• Mass: quantity of matter contained in
an object
• Inertia: tendency of a body to resist a
change in its state of motion
• Force: push or pull; the product of
mass & acceleration F = ma
• Net Force: resultant force derived from
the composition of two or more forces
Basic Concepts Related To
Kinetics
• Center of Gravity: point around which a
body’s weight & mass are equally
balanced in all directions
• Weight: attractive force that the earth
exerts on the body wt= mag
• Pressure: force per unit of area over
which the force acts p= F divided by A
N/cm2 , Pascals, or psi (lb/in2)
Basic Concepts Related To
Kinetics
• Volume: space occupied by a body;
cubic centimeters, cubic meters, liters
• Density: mass per unit of volume;
 = mass/volume
• Specific Weight: weight per unit of
volume; metric N/m3, English lb/ft3
• Torque: rotary effect of force
Basic Concepts Related To
Kinetics
• Impulse: product of force and the time
over which the force acts; Impulse = Ft
Size, Mass & Movement Forms
• Variety of life forms on earth: size,
shape and styles of locomotion
• Although this diversification of life forms
may seem to be arbitrary….this is far
from true
Size, Mass & Movement Forms
• There are highly systematic relationships
between:
– Body
– Body
– Body
– Body
mass and body surface
weight and lung volume
mass and heat production
mass and speed
• Basic geometric relations are
fundamental for form and function (see
example of cubes)
Size, Mass & Movement Forms
• Some physiological processes depend
on the area of body, others depend on
the body’s volume
– Air resistance is a function of surface
Body Size, Energetics &
Movement Forms
• Size is a key factor for:
– energetics
– movement speed
– gait patterns
• Respiratory System:
– small insects: diffusion of oxygen
– large mammals: development of lungs &
blood circulation (active pumping of O2
Body Size, Energetics &
Movement Forms
• Chain of connection:
– size of animal ==> type of respiration
system ==> basic metabolic rate ==>
maximum oxygen uptake ==> energetics
==> movement speed ==> movement
patterns
Body Size, Energetics &
Movement Forms
• Relationship between Energetics and
Mass:
– basic metabolic rate is proportional to body
mass
– for different locomotory activities there is a
systematic relationship between body mass
and energy cost
Body Size, Energetics &
Movement Forms
• Movement Speed and Gait Patterns
– 4-legged animals: 3 gaits, transitions are
always from walk to trot to gallop
– 2-legged animals: efficient and maximal
locomotory speed is determined
Lessons
• Movement forms are not chosen
arbitraryily
• Fundamental physical relationships,
e.g., size and mass, determine basic
energetic balance
• Fundamental energetic capabilities
determine locomotory forms
Lessons
• Preferred movement forms tend to
maximize efficiency
• Size and mass constrain movement
forms
Size, Mass & Development
• During the development of human
infants there are systematic changes in
relative proportions (see overhead)