Chapter 11 The Description of Human Motion KINESIOLOGY

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Chapter 11: The Description of Human Motion KINESIOLOGY Scientific Basis of Human Motion, 11

Chapter 11: The Description of Human Motion KINESIOLOGY Scientific Basis of Human Motion, 11 th edition Hamilton, Weimar & Luttgens Presentation Created by TK Koesterer, Ph. D. , ATC Humboldt State University Revised by Hamilton & Weimar © 2008 Mc. Graw-Hill Higher Education. All Rights Reserved.

Objectives 1. Name the motions experienced by the human body, and describe the factors

Objectives 1. Name the motions experienced by the human body, and describe the factors that cause & modify motion. 2. Name & properly use terms that describe linear & rotary 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 & rotary movement, & explain significance to human motion. 6. Identify kinematic components used to describe skillful performance of a motor task. © 2008 Mc. Graw-Hill Higher Education. All Rights Reserved.

Relative Motion • Motion is the act or process of changing place or position

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 plane: – At rest in reference to the plane. – In motion in reference to the earth. © 2008 Mc. Graw-Hill Higher Education. All Rights Reserved.

Cause of Motion • The cause of motion is a form of force. •

Cause of Motion • The cause of motion is a 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. © 2008 Mc. Graw-Hill Higher Education. All Rights Reserved.

Kinds of Motion • Although the variety of ways in which objects move appears

Kinds 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: – Translatory or linear – Rotary or angular © 2008 Mc. Graw-Hill Higher Education. All Rights Reserved.

Translatory Movement • An object is translated as a whole from one location to

Translatory Movement • An object is translated as a whole from one location to another. – Rectilinear: straight-line progression – Curvilinear: curved translatory movement Curvilinear motion Fig 11. 1 Rectilinear motion Fig 11. 2 © 2008 Mc. Graw-Hill Higher Education. All Rights Reserved.

Circular Motion • A special form of curvilinear motion. • Object moves along the

Circular Motion • A 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. © 2008 Mc. Graw-Hill Higher Education. All Rights Reserved.

Rotary, or Angular, Motion • Typical of levers, wheels, & axles • Object acting

Rotary, or Angular, 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 © 2008 Mc. Graw-Hill Higher Education. All Rights Reserved.

Rotary, or Angular, Motion • Circular motion describes motion of any point on the

Rotary, or Angular, 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 fashion – ball is moving with circular motion. – arm acts as a radius moving with angular motion. © 2008 Mc. Graw-Hill Higher Education. All Rights Reserved.

Other Movement Patterns • Combination of rotary & translatory is called general motion •

Other Movement Patterns • Combination of rotary & translatory is called general motion • Angular motions of forearm, upper arm & legs. • Hand travels linearly and imparts linear force to the foil Fig 11. 4 © 2008 Mc. Graw-Hill Higher Education. All Rights Reserved.

Kinds of Motion Experience by the Body • Most joints are axial. • Segments

Kinds of Motion Experience by the Body • Most joints are axial. • Segments undergo primarily angular motion. • Slight translatory motion in gliding joints. Fig 11. 5 © 2008 Mc. Graw-Hill Higher Education. All Rights Reserved.

Kinds of Motion Experience by the Body • Rectilinear movement when the body is

Kinds of Motion Experience by the Body • Rectilinear movement when the body is acted on by the force of gravity or a linear external force Fig 11. 7 Fig 11. 6 © 2008 Mc. Graw-Hill Higher Education. All Rights Reserved.

Kinds of Motion Experience by the Body • General motion – e. g. forward

Kinds of Motion Experience by the Body • General 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 © 2008 Mc. Graw-Hill Higher Education. All Rights Reserved.

Factors that Determine the Kind of Motion • Depends primarily on the kind of

Factors that Determine the Kind of Motion • Depends 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 translatory or rotary motion. – Determined by where force is applied in reference to its center of gravity. – Presence or absence of modifying forces. © 2008 Mc. Graw-Hill Higher Education. All Rights Reserved.

Factors Modifying Motion • External factors – Friction helps a runner gain traction, but

Factors Modifying Motion • External 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. © 2008 Mc. Graw-Hill Higher Education. All Rights Reserved.

Factors Modifying Motion • Internal or anatomical factors: – friction in joints; tension of

Factors Modifying Motion • Internal 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. • One of the major problems in movement is – How to take advantage of these factors. – How to minimize them when they are detrimental to the movement. © 2008 Mc. Graw-Hill Higher Education. All Rights Reserved.

KINEMATIC DESCRIPTION OF MOTION Linear Kinematics • Distance – How far an object has

KINEMATIC DESCRIPTION OF MOTION Linear Kinematics • Distance – How far an object has moved or traveled. • Displacement – Distance an object has moved from a reference point. – May not indicate how far object traveled. – A vector quantity having both magnitude and direction. © 2008 Mc. Graw-Hill Higher Education. All Rights Reserved.

Linear Kinematics • Walk north 3 km, then east 4 km. • What is

Linear Kinematics • Walk north 3 km, then east 4 km. • What is the distance traveled? • What is the displacement? Fig 11. 8 © 2008 Mc. Graw-Hill Higher Education. All Rights Reserved.

Speed and Velocity • Speed is how fast an object is moving, nothing about

Speed and Velocity • Speed is how fast an object is moving, nothing about the direction of movement. – a scalar quantity Average Speed = distance traveled or d time t © 2008 Mc. Graw-Hill Higher Education. All Rights Reserved.

Speed and Velocity • Velocity involves direction as well as speed – speed in

Speed and Velocity • Velocity involves direction as well as speed – speed in a given direction – rate of displacement – a vector quantity Average Velocity = displacement or s / t time v=s/t © 2008 Mc. Graw-Hill Higher Education. All Rights Reserved.

Acceleration • The rate of change in velocity. • May be positive or negative.

Acceleration • The 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 velocity time a = (vf – vi)/t © 2008 Mc. Graw-Hill Higher Education. All Rights Reserved.

Acceleration Fig 11. 10 Section a: Section b: Section c: Section d: v- increasing

Acceleration Fig 11. 10 Section a: Section b: Section c: Section d: v- increasing (+) v- constant (+) v- non-linear increase (+) v- decreasing (+) a-constant (+) a-zero a- non-constant (+) a- constant (-) © 2008 Mc. Graw-Hill Higher Education. All Rights Reserved.

Acceleration Units a = (final velocity – initial velocity) / time a = (final

Acceleration Units a = (final velocity – initial velocity) / time a = (final m/sec – initial m/sec) / sec a = (m/sec) / sec a = m/sec 2 © 2008 Mc. Graw-Hill Higher Education. All Rights Reserved.

Uniformly Accelerated Motion • • Constant acceleration rate. Common with freely falling objects. Air

Uniformly Accelerated Motion • • Constant acceleration rate. 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. © 2008 Mc. Graw-Hill Higher Education. All Rights Reserved.

Acceleration of Gravity • 32 ft/sec 2 or 9. 8 m/sec 2 • Velocity

Acceleration of Gravity • 32 ft/sec 2 or 9. 8 m/sec 2 • Velocity will increase 9. 8 m/sec every second when an object is dropped from some height. – End of 1 sec = 9. 8 m/sec – End of 2 sec = 19. 6 m/sec – End of 3 sec = 29. 4 m/sec • Does not consider resistance or friction of air. © 2008 Mc. Graw-Hill Higher Education. All Rights Reserved.

Air Resistance • Lighter objects will be affected more: – may stop accelerating (feather)

Air Resistance • Lighter 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. © 2008 Mc. Graw-Hill Higher Education. All Rights Reserved.

Laws of Uniformly Accelerated Motion • Distance traveled & downward velocity can be determined

Laws of Uniformly Accelerated Motion • Distance traveled & downward velocity can be determined for any point in time: vf = vi + at s = vi t + /2 at 2 vf 2 = vi 2 + 2 as Where: vf = final velocity vi = initial velocity a = acceleration t = time s = displacement © 2008 Mc. Graw-Hill Higher Education. All Rights Reserved.

Laws of Uniformly Accelerated Motion • Time it takes for an object to rise

Laws of Uniformly Accelerated Motion • Time 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 opposite. • Upwards velocities are positive. • Downward velocities are negative. © 2008 Mc. Graw-Hill Higher Education. All Rights Reserved.

Projectiles • Objects given an initial velocity and released. • Gravity is the only

Projectiles • Objects given an initial velocity and released. • Gravity is the only influence after release. * • Maximum horizontal displacement – e. g. long jumper, shot-putter • Maximum vertical displacement – e. g. high jumper, pole vault • Maximum accuracy – e. g. shooting in basketball or soccer * Neglecting air resistance. © 2008 Mc. Graw-Hill Higher Education. All Rights Reserved.

Projectiles • Follows a predictable path, a parabola. • Gravity will – slow upward

Projectiles • Follows a predictable path, a parabola. • Gravity will – slow upward motion. – increase downward motion. – at 9. 8 m/sec 2 Fig 11. 11 © 2008 Mc. Graw-Hill Higher Education. All Rights Reserved.

Projectiles Upward portion © 2008 Mc. Graw-Hill Higher Education. All Rights Reserved.

Projectiles Upward portion © 2008 Mc. Graw-Hill Higher Education. All Rights Reserved.

Projectiles Downward portion © 2008 Mc. Graw-Hill Higher Education. All Rights Reserved.

Projectiles Downward portion © 2008 Mc. Graw-Hill Higher Education. All Rights Reserved.

Projectiles • Initial velocity at an angle of projection: – Components • Vertical velocity:

Projectiles • Initial velocity at an angle of projection: – Components • Vertical velocity: affected by gravity • Horizontal velocity: not affected by gravity Fig 11. 12 © 2008 Mc. Graw-Hill Higher Education. All Rights Reserved.

Projectiles with Horizontal Velocity • One object fall as another object is projected horizontally.

Projectiles with Horizontal Velocity • One object fall as another object is projected horizontally. • Which will hit the ground first? Gravity acts on both objects equally Horizontal velocity projects the object some distance from the release point © 2008 Mc. Graw-Hill Higher Education. All Rights Reserved.

Projectiles with Vertical Velocity • To affect time an object is in the air

Projectiles 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. © 2008 Mc. Graw-Hill Higher Education. All Rights Reserved.

Projectiles with Vertical and Horizontal Velocities • This is the case for most projectiles.

Projectiles 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 © 2008 Mc. Graw-Hill Higher Education. All Rights Reserved.

Horizontal Distance of a Projectile • Depends on horizontal velocity & time of flight.

Horizontal Distance of a Projectile • Depends 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. © 2008 Mc. Graw-Hill Higher Education. All Rights Reserved.

Angle of Projection • Complementary angles of projection will have the same landing point:

Angle of Projection • Complementary angles of projection will have the same landing point: – A&B – C&D – 450 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 © 2008 Mc. Graw-Hill Higher Education. All Rights Reserved.

Factors that Control the Range of a Projectile 1. Velocity of Release 2. Angle

Factors that Control the Range of a Projectile 1. Velocity of Release 2. Angle of Projection 3. Height of Release 4. Height at Landing © 2008 Mc. Graw-Hill Higher Education. All Rights Reserved.

Angular Kinematics • Similar to linear kinematics. • Also concerned with displacement, velocity, and

Angular Kinematics • Similar to linear kinematics. • Also concerned with displacement, velocity, and acceleration. • Important difference is that they relate to rotary rather than to linear motion. • Equations are similar. © 2008 Mc. Graw-Hill Higher Education. All Rights Reserved.

Angular Displacement • Skeleton is a system of levers that rotate about fixed points

Angular Displacement • Skeleton is a system of levers that rotate about fixed points when force is applied. • Particles near axis have displacement less than those farther away. • Units of a circle: – Circumference = C C = 2πr – Radius = r – Constant (3. 1416) = π © 2008 Mc. Graw-Hill Higher Education. All Rights Reserved.

Units of angular Displacement • Degrees: – Used most frequently • Revolutions: – 1

Units of angular Displacement • Degrees: – Used most frequently • Revolutions: – 1 revolution = 360º = 2π radians • Radians: – 1 radian = 57. 3° – Favored by engineers & physicists – Required for most equations • Symbol for angular displacement - (theta) © 2008 Mc. Graw-Hill Higher Education. All Rights Reserved.

Angular Velocity = /t • Rate of rotary displacement - (omega). • Equal to

Angular Velocity = /t • Rate of rotary displacement - (omega). • Equal to the angle through which the radius turns divided by time. • Expressed in degrees/sec, radians/sec, or revolutions/sec. • Called average velocity because angular displacement is not always uniform. • The longer the time span of the measurement, the more variability is averaged. © 2008 Mc. Graw-Hill Higher Education. All Rights Reserved.

Angular Velocity • High-speed video: • 150 frames / sec =. 0067 sec /

Angular Velocity • High-speed video: • 150 frames / sec =. 0067 sec / picture • Greater spacing, greater velocity. • “Instant” velocity between two pictures: a = 1432° / sec b = 2864° /sec Fig 11. 16 © 2008 Mc. Graw-Hill Higher Education. All Rights Reserved.

Angular Acceleration = ( f - i)/ t • (alpha) is the rate of

Angular Acceleration = ( f - i)/ t • (alpha) is the rate of change of angular velocity and expressed by above equation. – f is final velocity – i is initial velocity © 2008 Mc. Graw-Hill Higher Education. All Rights Reserved.

Angular Acceleration • a is 25 rad/sec • b is 50 rad/sec • Time

Angular Acceleration • a is 25 rad/sec • b is 50 rad/sec • Time lapse = 0. 11 sec Fig 11. 16 = f - i / t = (50 – 25) / 0. 11 = 241 rad/sec Velocity increases by 241 radians per sec each second. © 2008 Mc. Graw-Hill Higher Education. All Rights Reserved.

Relationship Between Linear and Angular Motion • Lever PA > PB > PC •

Relationship Between Linear and Angular Motion • Lever PA > PB > PC • All move same angular distance in the same time. Fig 11. 17 © 2008 Mc. Graw-Hill Higher Education. All Rights Reserved.

Relationship Between Linear and Angular Motion • • Angular to linear displacement: s =

Relationship Between Linear and Angular Motion • • Angular to linear displacement: s = r C traveled farther than A or B, in the same time. C had a greater linear velocity than A or B. All three have the same angular velocity, but the linear velocity of the circular motion is proportional to the length of the lever. • If angular distance is constant, the longer the radius, the greater is the linear velocity of a point at the end of that radius. © 2008 Mc. Graw-Hill Higher Education. All Rights Reserved.

Relationship Between Linear and Angular Motion • The reverse is also true. • If

Relationship Between Linear and Angular Motion • The reverse is also true. • If linear velocity is constant, an increase in radius will result in a decrease in angular velocity, and vice versa. Fig 11. 18 © 2008 Mc. Graw-Hill Higher Education. All Rights Reserved.

Relationship Between Linear and Angular Motion • If one starts a dive in an

Relationship Between Linear and Angular Motion • If one starts a dive in an open position and tucks tightly, angular velocity increases. – Radius of rotation decreases. – Linear velocity does not change. • Shortening the radius will increase the angular velocity, and lengthening it will decrease the angular velocity. © 2008 Mc. Graw-Hill Higher Education. All Rights Reserved.

Relationship Between Linear and Angular Motion • The relationship between angular velocity and linear

Relationship Between Linear and Angular Motion • The relationship between angular velocity and linear velocity at the end of its radius is = r expressed by • Equation shows the direct proportionality that exists between linear velocity and the radius. © 2008 Mc. Graw-Hill Higher Education. All Rights Reserved.

Chapter 11: The Description of Human Motion © 2008 Mc. Graw-Hill Higher Education. All

Chapter 11: The Description of Human Motion © 2008 Mc. Graw-Hill Higher Education. All Rights Reserved.