1. CHAPTER 4 AN INTRODUCTION TO BIOMECHANICS

2. Biomechanics Biomechanics is the study of how and why the human body moves. Biomechanics is the study of how and why the human body moves. It investigates how the physical laws of mechanics apply to the human body. It investigates how the physical laws of mechanics apply to the human body. Role of biomechanist: analyse an athletes performance in order to improve technique, improve equipment design and reduce injuries. Role of biomechanist: analyse an athletes performance in order to improve technique, improve equipment design and reduce injuries. –Quantitative Analysis: use of numbers (eg speed / distance / time) –Qualitative Analysis: description without numbers (eg bend your knees Checkpoints: Page 95 – Q.1,3 Checkpoints: Page 95 – Q.1,3

3. Principles of Biomechanics CD-ROM: CD-ROM: –Overview –Inertia –Mass –Force  Types of forces –Newtons Laws of Motion Velocity: (page 98) Velocity: (page 98) –What does velocity measure? –What are its two important characteristics? Read: Reality PE Snapshots (Page 99) Read: Reality PE Snapshots (Page 99) –Radar equipment!

4. Principles (cont) CD-ROM: CD-ROM: –Impulse Checkpoints: (page 102) Checkpoints: (page 102) –Questions: 1, 2, 4, 5 Acceleration: (Newton’s 2 nd law) Acceleration: (Newton’s 2 nd law) –What is acceleration? –How do you calculate acceleration? Conservation of momentum: (Newtons 3 rd law) Conservation of momentum: (Newtons 3 rd law) –What is this principle? –Give an example of how this principle works? Elasticity: Elasticity: –What does the term elasticity mean? Explain two ways in which a tennis player can generate more velocity through elasticity.

5. Principles (cont) Summation of Momentum: Summation of Momentum: –Define summation of momentum? –When does effective summation of momentum take place? CD-ROM: CD-ROM: –Friction Checkpoints: (page 112) Checkpoints: (page 112) –Questions 3, 5, 6

6. Balance and Stability Read pages 113-118 Read pages 113-118 Define the terms Balance and Stability? Define the terms Balance and Stability? What factors affect balance and stability? What factors affect balance and stability? Explain the difference between static and dynamic balances? Explain the difference between static and dynamic balances? What is meant by the ‘centre of gravity’ and how does it change when you change your body position? What is meant by the ‘centre of gravity’ and how does it change when you change your body position? How does the mass of a person affect their stability? How does the mass of a person affect their stability? CD-ROM: Recap of balance using CD examples. CD-ROM: Recap of balance using CD examples.

7. Basic movement patterns Striking Throwing StoppingRunning

8. Basic movement patterns StrikingThrowingRunningStopping Tennis Tennis Golf Golf Volleyballl Volleyballl Cricket Cricket Baseball Baseball Basketball Basketball Netball Netball Athletics Athletics Baseball Baseball Cricket Cricket Soccer Soccer Baseball Baseball Netball Netball Athletics Athletics Cycling Cycling

9. Biomechanical principles associated with basic movement patterns Striking - Golf Throwing - Baseball Running - Athletics Stopping - Netball Newtons laws (force) Newtons laws (force) levers levers momentum momentum impact impact stability stability projectile motion projectile motion flattening the arc flattening the arc summation of momentum summation of momentum accuracy accuracy forces (action/ reaction) forces (action/ reaction) motion (straight line) motion (straight line) momentum momentum friction friction forces forces acceleration and deceleration acceleration and deceleration Newtons laws Newtons laws friction friction

10. Tennis

11. Biomechanical principles associated with tennis Forces Forces Levers Levers Torque Torque Velocity Velocity Power Power Acceleration Acceleration Deceleration Deceleration Projectile motion Projectile motion Momentum Momentum Elasticity Elasticity Coefficient of restitution Coefficient of restitution Spin Spin Centre of gravity Centre of gravity Base of support Base of support Accuracy Accuracy Mass Mass Inertia Inertia Motion Motion Impulse Impulse

12. Tennis Force (Newtons N) Force (Newtons N) –A push or a pull –What effect does a force have on an object? Starts, stops, speeds up, slows down, changes direction. It changes an objects velocity Velocity (ms -1 ) Velocity (ms -1 ) – displacement / time

13. Mass (kg) Mass (kg) –Amount of matter in an object –Weight is an indirect measure of mass Acceleration (ms -2 ) Acceleration (ms -2 ) - change in velocity / time - final velocity – initial velocity time

14. Newtons laws 1.A body continues in its state of rest or of uniform motion in a straight line unless it is compelled to change that state by forces acting on it. 2.The acceleration of an object is directly proportional to the net force applied and inversely proportional to its mass. F = ma 3.For every action the is an equal and opposite reaction.

15. Momentum Momentum (kg ms -1) Momentum (kg ms -1) - p = mv - two objects travelling at the same velocity, the one with the greater mass will have the greater momentum and vice versa, two objects of the same mass, the one travelling at a greater velocity will have a greater momentum. - momentum is always conserved

16. Impulse Impulse –Change in momentum –I =  p OR I = Ft –Impulse can be increased by increasing the force applied or increasing the time over which the force is applied. –When a mass is constant, a change in impulse will result in a greater release velocity of the object (ball)

17. Summation of momentum Summation of momentum –Used to maximise the speed of the racquet head –Works when the larger slower body parts begin the movement and move sequentially through until the smaller and quicker finish the movement. –See laboratory

18. Elasticity Elasticity –The ability of an object to return to its original shape –The more quickly an object does this the less energy it looses –Coefficient of restitution is a measure of an objects elasticity e = height bounced height dropped height dropped –String tension determines how much contact time the ball has with the racquet

19. Levers Levers –Classes of levers –Factors that affect the use of external levers  Length of levers  Inertia of the lever  Force Compare and contrast techniques (elite and novice) Compare and contrast techniques (elite and novice) Evaluate performance using biomechanical principles Evaluate performance using biomechanical principles