Biomechanical Principles: Newton's Laws and Motion Types

1. SECTION 15 Biomechanical Principles and Applications

2. Presentation Outline • Sir Isaac Newton’s Three Laws of Motion • Types of Motion • Key terms in biomechanics • Definition of biomechanics and biomechanical principles

3. Isaac Newton’s “3 Laws of Motion” • 1. The Law of Inertia • 2. The Law of Acceleration • 3. The Law of Reaction

4. Isaac Newton’s “3 Laws of Motion” • 1. The Law of Inertia • An object at rest tends to stay at rest and an object in motion tends to stay in motion (unless an external force is applied eg. friction or gravity).

5. Isaac Newton’s “3 Laws of Motion” • 2. The Law of Acceleration • A force applied to a body causes an acceleration proportional to the force, in the direction of the force, and inversely proportional to the body’s mass. • F = MA

6. Isaac Newton’s “3 Laws of Motion” • 2. The Law of Acceleration

7. Isaac Newton’s “3 Laws of Motion” • 3. The Law of Reaction • For every action there is an equal and opposite reaction.

8. Types of Motion • It is important to distinguish between two types of motion: • Linear (or Translational) Motion • Movement in particular direction. Example: a sprinter accelerating down the track. • Rotational Motion • Movement about an axis. The force does not act through the centre of mass, but rather is “off-centre,” and this results in rotation. Example: ice-skater’s spin.

9. Rotational Motion (Angular) • Most human movements are rotational ie they take place around an axis.

10. Rotational Motion (Angular) • Most human movements are rotational ie they take place around an axis.

11. Rotational Motion (Angular) • When we impart spin on a ball, it’s due to a force applied away from the CoM. • What kind of pitch occurs if the force is applied through the ball’s CofM?

12. Centre of Mass (Gravity) • The point on an object where it’s mass is most concentrated. (the point where that body would balance on a very small base)

13. Centre of Mass (Gravity) • Important concept when stability is important • If a force is applied through the CoM, linear motion results • If a force is applied at a distance to the CoM, Rotation or Angular motion occurs.

14. Seven Principles of Biomechanical Analysis • The Coaching Association of Canada’s National Coaching Certification Program (NCCP) Level 2 Theory course sets forward seven principles that can be grouped into four broad categories: • (1) stability, • (2) maximum effort, • (3) linear motion, and • (4) angular motion.

15. Seven Principles of Biomechanical Analysis • STABILITY • Principle 1: The lower the centre of mass, the larger the base of support, the closer the centre of mass to the base of support, and the greater the mass, the more stability increases. • Four subcomponents • Example: Sumo wrestling

16. Stability • Often the Low man wins in football

17. Stability • Is this a stable position? Why or why not?

18. Stability Which position is more stable? Why?

19. Unstable Balance • Sometimes athletes need to be balanced but ready to move quickly ie unstable • Eg. Sprint start, receiving serve in tennis, swim start

20. Unstable Balance • What makes This unstable?

21. Seven Principles of Biomechanical Analysis • MAXIMUM EFFORT • Principle 2: The production of maximum force requires the use of all possible joint movements that contribute to the task’s objective. • Examples: golf, bench press, sprint start

22. REVIEW • Name Newton’s 3 Laws of Motion!

23. Seven Principles of Biomechanical Analysis • MAXIMUM VELOCITY • Principle 3: The production of maximum velocity requires the use of joints in order – from largest to smallest. • Examples: hockey slapshot, hitting a golf ball

24. Seven Principles of Biomechanical Analysis • LINEAR MOTION • Principle 4: The greater the applied impulse, the greater the increase in velocity. • Range of Motion (ROM) important • Example: spiking a volleyball

25. Seven Principles of Biomechanical Analysis • LINEAR MOTION • Principle 5: Movement usually occurs in the direction opposite that of the applied force. • Examples: basketball, kicking

26. Seven Principles of Biomechanical Analysis • ANGULAR MOTION • Principle 6: Angular motion is produced by the application of a force acting at some distance from an axis, that is, by torque. • Principle is also known as the principle of the production of angular motion • Example: diving

27. Examples of Rotation Principles • Diving • After leaving the high diving board, the diver curls tightly and then opens up just before entering the water. By opening up before entry, the diver increases the moment of inertia, thereby slowing down the angular velocity.

28. Examples of Rotation Principles • Ice-Skating • The ice-skater begins to spin with arms spread apart then suddenly brings them closer to the body. The end result of tightening up is that the skater’s spin (angular velocity) increases, seemingly miraculously.

29. Examples of Rotation Principles • Gymnastics • By opening up, the gymnast increases the moment of inertia (radius of rotation), thereby resulting in a decrease in angular velocity.

30. Seven Principles of Biomechanical Analysis • ANGULAR MOMENTUM • Principle 7: Angular momentum is constant when an athlete or object is free in the air. • This principle is also known as the principle of conservation of angular momentum, and its key component is the fact that, once an athlete is airborne, he or she will travel with constant angular momentum. • Example: Diver, gymnast,

31. Conservation of Momentum • This is evident in figure skating on ice which has very low friction. Angular momentum = radius of rotation x rotational velocity

32. Conservation of Momentum • Angular momentum = radius of rotation x angular speed • If the skater increases her radius then her angular speed will decrease to keep momentum conserved.

33. Conservation of Energy • The conservation of energy principle states that energy can never be created or destroyed, but can only be converted from one form to another.

34. 5 Phases of a Sport Skill • Used to bring a skill down into smaller parts • Helps coaches to detect and correct errors • Key Points are “look fors” that coaches use to produce ideal mechanics/performanc

35. Five Phases • Preliminary Movements • Backswing/Recovery • Force Producing Movements • Critical Instant • Follow-Through

36. 5 Phases of a Sport Skill Preliminary Movements Key Points • Pick a Target • Open stance • Hold Ball with Opposite Hand • Hold the Ball at Waist Height • Eye on the Ball

37. 5 Phases of a Sport Skill(Soccer Punt) Preliminary Movements Key Points • Pick a Target • Open stance • Hold Ball with Opposite Hand • Hold the Ball at Waist Height • Eye on the Ball

38. 5 Phases of a Sport Skill Backswing/Recovery Key Points • Eye on the ball • Maintain good posture • Large last step • Ankle locked

39. 5 Phases of a Sport Skill Force Producing Movements Key Points • Eye on the ball • Maintain good posture • Largest muscles to the smallest • Use arm for balance • Open the hips up

40. 5 Phases of a Sport Skill Critical Instant Key Points • Eye on the ball • Contact with hardest part of the foot • Lock your kicking foot upwards • Let ball fall below knee height • Lock your leg

41. 5 Phases of a Sport Skill Follow-Through Key Points • Be smooth and fluid • Foot carries on towards target • Eyes follow ball to target

42. 5 Phases of a Sport Skill

43. Phases of a Skill 1. Preliminary movements 2. Backswing 3. Force producing movements 4. Critical Instant 5. Follow through

44. 5 Phases of a Sport Skill • Badminton Smash – slow motion • Badminton Smash

45. That’s It!