CHAPTER 11:PART 1 THE DESCRIPTION OF HUMAN MOTION KINESIOLOGY Scientific Basis of Human Motion, 12...
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Transcript of CHAPTER 11:PART 1 THE DESCRIPTION OF HUMAN MOTION KINESIOLOGY Scientific Basis of Human Motion, 12...
CHAPTER 11:PART 1THE DESCRIPTION OF
HUMAN MOTION
CHAPTER 11:PART 1THE DESCRIPTION OF
HUMAN MOTION
KINESIOLOGYScientific Basis of Human Motion, 12th edition
Hamilton, Weimar & LuttgensPresentation Created by
TK Koesterer, Ph.D., ATCHumboldt State University
Revised by Hamilton & Weimar
Copyright © 2012 by The McGraw-Hill Companies, Inc. All rights reserved.McGraw-Hill/Irwin
11A-2
ObjectivesObjectives1. Name the motions experienced by the human body,
and describe the factors that cause & modify motion.
2. Name & properly use terms that describe linear & angular motion.
3. Explain the interrelationship that exist among displacement, velocity, & acceleration, & use them to describe & analyze human motion.
4. Describe behavior of projectiles, & explain how angle, speed, & height of projection affect that behavior.
5. Describe relationship between linear & angular movement, & explain significance to human motion.
6. Identify kinematic components used to describe skillful performance of a motor task .
11A-3
Motion: Relative MotionMotion: Relative Motion
Motion is the act or process of changing place or position with respect to some reference object.At rest or in motion depends totally on
the reference.Sleeping passenger in a flying
airplane:At rest in reference to the airplane.In motion in reference to the earth.
11A-4
Cause of MotionCause of Motion
The cause of motion is some form of force.
Force is the instigator of movement.Force must be sufficiently great to
overcome the object’s inertia, or resistance to motion.
Force relative to resistance will determine if the object will move or remain at rest.
11A-5
Kinds of MotionKinds of Motion
Although the variety of ways in which objects move appears to be almost limitless, careful consideration reveals only two classifications of movement patterns:Linear or translatory Angular or rotary
11A-6
Translatory MovementTranslatory Movement
An object is translated as a whole from one location to another.Rectilinear: straight-line progressionCurvilinear: curved translatory
movement
Fig 11.1 Fig 11.2
Rectilinear Rectilinear motionmotion
CurvilinearCurvilinearmotionmotion
11A-7
Circular MotionCircular MotionA special form of curvilinear motion.
Object moves along the circumference of a circle, a curved path of constant radius.
The logic relates to the fact that an unbalanced force acts on the object to keep it in a circle .
If force stops acting on the object, it will move in a linear path tangent to the direction of movement when released.
11A-8
Angular, or Rotary, MotionAngular, or Rotary, Motion
Typical of levers, wheels, & axles
Object acting as a radius moves about a fixed point.
Measured as an angle, in degrees.
Body parts move in an arc about a fixed point. Fig 11.3
11A-9
Angular, or Rotary, MotionAngular, or Rotary, Motion
Circular motion describes motion of any point on the radius.
Angular motion is descriptive of motion of the entire radius.
When a ball is held as the arm moves in a windmill fashionball is moving with circular motion.arm acts as a radius moving with angular
motion.
11A-10
Other Movement PatternsOther Movement PatternsCombinations of linear & angular motion
are called general motion
Angular motions of forearm, upper arm & legs.
Hand travels linearly and imparts linear force to the foil.
Fig 11.4
11A-11
Kinds of Motion Experienced by the BodyKinds of Motion Experienced by the Body
Most joints are axial.
Segments undergo primarily angular motion.
Slight translatory motion in gliding joints.
Fig 11.5
11A-12
Kinds of Motion Experienced by the BodyKinds of Motion Experienced by the Body
Linear movement when the body is acted on by the force of gravity or a linear external force.
Fig 11.7Fig 11.6
11A-13
Kinds of Motion Experienced by the BodyKinds of Motion Experienced by the BodyGeneral motion
e.g. forward and backward rolls on ground
Rotary motion e.g. spinning on ice skates
Curvilinear translatory motion e.g. diving and jumping
Reciprocating motion e.g. swinging on a swing
11A-14
Factors that Determine the Kind of MotionFactors that Determine the Kind of MotionDepends primarily on the kind of motion
permitted in a particular object.Lever permits only angular motion.Pendulum permits only oscillatory motion.
If an object is freely movable, it permits either linear or angular motion.Determined by where force is applied in
reference to its center of gravity.Presence or absence of modifying forces.
11A-15
Factors Modifying MotionFactors Modifying MotionExternal factors
Friction helps a runner gain traction, but hinders the rolling of a ball.
Air resistance or wind is indispensable to the sailboat’s motion, but may impede a runner.
Water resistance is essential for propulsion, yet it hinders an objects’ progress through the water.
11A-16
Factors Modifying MotionFactors Modifying MotionInternal or anatomical factors:
Friction in joints; tension of antagonists, ligaments & fasciae; anomalies of bone & joint structure; atmospheric pressure inside joints; and presence of interfering soft tissues.
Major problems in movement are:How to take advantage of these factors.How to minimize them when they are
detrimental to the movement.
11A-17
Kinematic Description of MotionKinematic Description of Motion
DistanceHow far an object has traveled.
DisplacementDistance an object has moved from a
reference point. May not indicate how far object traveled.A vector quantity having both magnitude
and direction.
Linear KinematicsLinear KinematicsLinear KinematicsLinear Kinematics
11A-18
Linear Kinematics Linear Kinematics Walk north 3 km, then east 4 km.
What is the distance traveled?
What is the displacement?
Fig 11.8
11A-19
Speed and VelocitySpeed and Velocity
Speed is how fast an object is moving, without regard to the direction of movement.a scalar quantity
Average Speed = distance traveled or d
time t
11A-20
Velocity involves direction as well as speed.Speed in a given directionRate of displacementA vector quantity
Average Velocity = displacement or s time t
Speed and VelocitySpeed and Velocity
v s
t
11A-21
AccelerationAccelerationThe rate of change in velocity.May be positive or negative.If acceleration is positive then velocity will
increase.If acceleration is negative then velocity will
decrease.
Average acceleration = final velocity – initial velocitytime
a v f v it
orvt
11A-22
AccelerationAcceleration
Fig 11.10
Section a:
v- increasing (+)
a-constant (+)
Section b:
v- constant (+)
a-zero
Section c:
v- non-linear increase (+)
a- non-constant (+)
Section d:
v- decreasing (+)
a- constant (-)
11A-23
Acceleration UnitsAcceleration Units
a = (final velocity – initial velocity)/time
a = (final m/sec – initial m/sec)/sec
a = (m/sec)/sec
a = m/sec2
11A-24
Uniformly Accelerated MotionUniformly Accelerated Motion
Constant acceleration.Common with freely falling objects.Air resistance is neglected.Objects will accelerate at a uniform
rate due to acceleration of gravity.Object projected upward will be
slowed at the same uniform rate due to gravity.
11A-25
Acceleration Due to GravityAcceleration Due to Gravity
32 ft/sec2 or 9.8 m/sec2
Velocity will increase 9.8 m/sec every second when an object is dropped from some height. End of 1 sec = 9.8 m/secEnd of 2 sec = 19.6 m/secEnd of 3 sec = 29.4 m/sec
Does not consider resistance or friction of air.
11A-26
Air Resistance Air ResistanceLighter objects will be affected more:
may stop accelerating (feather) and fall at a constant rate.
Denser, heavier objects are affected less.
Terminal velocity: – Air resistance is increased to equal accelerating force of gravity. Object no longer accelerating, velocity stays
constant.Sky diver = approximately 120 mph or 53
m/sec.
11A-27
Laws of Uniformly Accelerated MotionLaws of Uniformly Accelerated Motion
Distance traveled & velocity can be determined for any point in time when acceleration is constant:
Where:vf = final velocity
vi = initial velocity
a = accelerationt = times = displacement
v f v i at
sv it at 2
2
v f v i2 2as
11A-28
Laws of Uniformly Accelerated MotionLaws of Uniformly Accelerated MotionTime it takes for an object to rise to the
highest point of its trajectory is equal to the time it takes to fall to its starting point.
Upward flight is a mirror image of the downward flight.
Release & landing velocities are equal, but in opposite directions.Upward velocities are positive.Downward velocities are negative.
11A-29
ProjectilesProjectilesObjects given an initial velocity and
released.
Gravity is the only influence after release.*
Maximum horizontal displacemente.g. long jumper, shot-putter
Maximum vertical displacemente.g. high jumper, pole vault
Maximum accuracye.g. shooting in basketball or soccer
* Neglecting air resistance.
11A-30
ProjectilesProjectiles
Follow a predictable path, a parabola.
Gravity will slow upward motion, increase downward motion.at 9.8 m/sec2.
Fig 11.11
11A-31
ProjectilesProjectilesUpward portion
Position versus TimeUpward
0
1
2
3
4
5
6
0 0.2 0.4 0.6 0.8 1 1.2
Time (sec)
Pos
ition
y-d
irect
ion
(m)
Velocity versus TimeUpward
0
2
4
6
8
10
0 0.2 0.4 0.6 0.8 1 1.2
Time (sec)
Vel
ocity
y-d
irect
ion
(m/s
)
Acceleration versus TimeUpward
-12
-10
-8
-6
-4
-2
0
0 0.2 0.4 0.6 0.8 1 1.2
Time (sec)
Acc
eler
atio
n y-
dire
ctio
n (m
/s2)
11A-32
ProjectilesProjectilesDownward portion
Position versus TimeDownward
0
1
2
3
4
5
6
0 0.2 0.4 0.6 0.8 1 1.2
Time (sec)
Pos
ition
y-d
irect
ion
(m)
Velocity versus TimeDownward
-10
-8
-6
-4
-2
0
0 0.2 0.4 0.6 0.8 1 1.2
Time (sec)
Vel
ocity
y-d
irect
ion
(m/s
)
Acceleration versus TimeDownward
-12
-10
-8
-6
-4
-2
0
0 0.2 0.4 0.6 0.8 1 1.2
Time (sec)
Acc
eler
atio
n y-
dire
ctio
n (m
/s2)
11A-33
ProjectilesProjectilesInitial velocity at an angle of projection:
ComponentsVertical velocity: affected by gravityHorizontal velocity: not affected by gravity
Fig 11.12
11A-34
Projectiles with Horizontal VelocityProjectiles with Horizontal Velocity
One object falls as another object is projected horizontally.• Which will hit the ground first?
Gravity acts on both objects equally
Horizontal velocity carries the object some distance from the release point
11A-35
Projectiles with Vertical VelocityProjectiles with Vertical Velocity
To affect time an object is in the air:vertical velocity must be added. height of release may be increased.
Upward velocity will: be slowed by gravity. reach zero velocity. gain speed towards the ground.at height of release object will have the
same velocity it was given at release.
11A-36
Projectiles with Vertical and Horizontal VelocitiesProjectiles with Vertical and Horizontal Velocities
This is the case for most projectiles.
Horizontal velocity remains constant.
Vertical velocity subject to uniform acceleration of gravity.
Fig 11.14
11A-37
Horizontal Distance of a ProjectileHorizontal Distance of a ProjectileDepends on horizontal velocity &
time of flight.Time of flight depends on maximum
height reached by the object.governed by vertical velocity of the object.
Magnitude of these two vectors determined by:initial velocity vector.angle of projection.
11A-38
Angle of ProjectionAngle of ProjectionComplementary angles of projection will
have the same landing point:A & BC & D450 angle (E)
Throwing events may have a lower angle of projection, because of a difference in height of release and height of landing.
Fig 11.15
11A-39
Factors that Determine the Range of a ProjectileFactors that Determine the Range of a Projectile
1. Velocity at release2. Angle of projection3. Height of release4. Height at landing