Transcript How Do I Move? - tpsexercisescience12

Kinematics Variables

Time: temporal characteristics of a performance, either of the total
skill or its phases

Displacement: length and direction of the path an athlete takes from
start to finish
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Angular Displacement: direction of, and smallest angular change
between, the rotating body’s initial and final position
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Velocity: displacement per unit of time
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Angular Velocity: angular displacement per unit of time
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Acceleration: rate of change of velocity
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Angular Acceleration: angular velocity per unit of time
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Kinetics Study of Motion

Focuses on the various forces that are associated with a movement
Internal Forces:

generated by muscles pulling via
their tendons on bones, and to
bone-on-bone forces exerted across
joint surfaces
External Forces:

acting from without, such as the
force of gravity or the force from
any body contact with the ground,
environment, sport equipment, or
opponent
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Human Body Models
Particle Model:
 Used when the object of interest (the human body or an
object) is airborne after being thrown, struck, or kicked
Stick Figure Model:
 Used when the object is in contact with its environment
Rigid Segment Model:
 Used for more sophisticated quantitative analyses
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Three models used to represent the diver
Particle Model
Stick Figure Model
Rigid Segment Model
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Types of Motion
Linear motion
General motion
Angular motion
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Linear Motion
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When all parts of the body move the same distance, in the same
direction, at the same time

Translation refers to movement of the body as a unit without
individual segment parts of the body moving relative to one another

Rectilinear motion occurs when movement follows a straight line

Curvilinear motion occurs when the movement path is curved
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Angular and General Motion
Angular Motion (rotation)

Occurs when a body moves along a
circular path, through the same angle,
in the same direction, and at the same
time

The axis of rotation is the point about
which movement occurs

All joint motions are angular motions
General Motion

A combination of linear and angular
motion

Includes most athletic and many
everyday activities
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Causes of motion

The only cause of motion of the human body is the
application of an external force

Force is any action, a push or pull, which tends to cause an object to
change its state of motion by experiencing an acceleration

Constant Velocity occurs when an object is not accelerating

Linear Motion is caused by forces which act through a body’s
centre of mass

Angular motion is caused by forces that do not go through the
centre of mass
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Linear motion results when the forces
are applied through the centre of mass
Angular motion results when the forces
are applied away from the centre of mass
Scalar and Vector Quantities
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Scalar quantities have only magnitude (time)
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Vector quantities have magnitude and direction (force)
- vectors are straight-line segments with one end defined
as the tail and the arrow tip defined as the head.
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Adding of Vectors
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
The head of a vector points in the direction of the quantity the vector
represents
Vectors can be added together using the head to tail method
- to add vector B to vector A, an identical vector is drawn (same length
and direction) as vector B beginning at the head of vector A
- the resultant vector is directed from the tail of vector A to the head of
vector B
a
a
+
b
b
Resultant
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Resultant
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Levers

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
Simple machines that augment the amount of work done by an applied
force
A rigid body (i.e., long bone) that rotates about a fixed point (i.e.,
joint) called a fulcrum (F)
Acting on the lever is a resistive force (R, i.e weight of a limb
segment) an an applied force (AF, i.e., muscle contraction).
Three classes of levers:
a. first class (teeter-totter)
b. second class (wheelbarrow)
c. third class (screen door with a spring closing)
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Factors affecting the moment of force
D
D
A. Balanced teeter-totter
B. Increasing the moment arm by leaning backwards
C. Increasing the applied force by adding a friend
Calculating net external force using free body diagrams