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Sport Biomechanics

Sport Biomechanics. Understanding how a skill is performed mechanically is an important stepping stone to understanding how it can be learned. Basic Laws of Biomechanics.

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Sport Biomechanics

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  1. Sport Biomechanics Understanding how a skill is performed mechanically is an important stepping stone to understanding how it can be learned.

  2. Basic Laws of Biomechanics • Sir Isaac Newton developed three laws to explain the relationship between forcesacting on a body and the motion of the body.

  3. What is a Force? • A force is a push or a pull. Forces are measured in Newtons. Did you know that forces only exist when objects interact!

  4. What is a Force? • A force gives energy to an object. Whenever two objects touch, forces are involved.

  5. What is a Force? • A force can cause acceleration, a change in direction or deceleration. A force is NOT required to keep an object in motion • Examples: -Drag, Friction, Thrust, Gravity, Weight, Magnestism

  6. Law 1: Law of Inertia • An object at rest will remand at rest unless acted upon by some external force. • The greater the inertia an object has the greater the force needed to move it.

  7. Law 1: Law of Inertia • In what sports would a lot of inertia be to the athletes advantage? -Sumo, Scrumming • In what sports would a lot of inertia be to the athletes disadvantage? • Sports requiring quick • change of direction

  8. Inertia & the Golf Swing • How does inertia affect the golf swing? Club Head Golf Ball

  9. Law 2: Law of Acceleration • When a force acts upon a mass, the result is acceleration of that mass. • The greater the force, the great the acceleration. • The smaller the mass, the greater the acceleration. • The mass will accelerate in the direction the force is applied. F = m x a (force) (mass) (acceleration)

  10. Assume that both steam engines below apply the same amount of force.

  11. Law 2: Law of Acceleration • How can we apply this law of acceleration to the golf swing? - The greater the initial force (contracting muscles), the greater the acceleration of the club head and the greater acceleration on the golf ball on contact. - The greater the force, the further the golf ball will travel.

  12. Law 3: Action - Reaction Law • For every action, there is an equal and opposite reaction. • When we apply a force this is known as an action force. • The object we apply the force to, applies a force back, this is a reaction force.

  13. Law 3: Action - Reaction Law • These two forces always work in pairs, and are opposite in direction and equal in size.

  14. The forces here are equal and opposite. Neither the dog nor its owner pulls with greater force. They pull with the same force in opposite directions

  15. The forces will be equal when the truck crashes into the car. Since the car is smaller, the car will have a greater acceleration.

  16. If forces are always equal and opposite, how can anything move? Here is a famous problem:A horse is pulling on a cart, and the cart pulls back with the same amount of force. If all forces are equal, how can the horse and cart move? Answer: The horse moves because the force he exerts with his hooves is greater than the force of the wagon pulling him back.

  17. If forces are always equal and opposite, how can anything move? • What forces act on the cart? The horse pulls it forward, and there is a backward force from the ground: friction. If the horses' pull exceeds the friction of the cart, it will accelerate. Acceleration will occur if one force pair (push of ground/push of horse) is greater than another force pair (friction/pull of cart).

  18. If forces are always equal and opposite, how can anything move? Example 2: If the person's friction forces against the floor are greater than the refrigerator's friction forces, the fridge will accelerate.

  19. Motion

  20. General Motion Angular Motion Types of Motion Curvilinear Motion Linear Motion

  21. Linear Motion • When all parts of the body move in a straight parallel lines (same distance in same time). • Examples -Dropping a ball -Sliding in to first base -Tobogganing down a hill

  22. Curvilinear motion • When all parts of the body move in a curved path along parallel lines. • Examples -free fall sky diving -path of a tennis serve -flight of golf ball

  23. Angular Motion • Rotation about an axis that can be either internal or external. • Examples -swinging around a high bar -a bicep curl -a golf swing

  24. General Motion • Linear motion of the body as a result of angular motion of other parts of the body. • Examples • Cycling • Swimming • Kayaking

  25. Projectile Motion Any object released into the air is termed a projectile.

  26. All projectiles have a flight path and flight time depending on how they affected by the variables below. • Gravity • Air Resistance • Angle of Release • Speed of Release • Height of Release • Spin

  27. Gravity • Gravity acts on a body to give it mass. • The greater the mass of an object the greater the influence of gravity upon it. • What is the effect of gravity on a projectile? - It decreases the height a projectile can attain.

  28. Gravity

  29. Gravity

  30. Air Resistance • Air resistance acts on the horizontal component of a projectiles path.

  31. Angle of Release • The angle of release of a projectile determines the flight path. • If the angle of release is high, the projectile has a longer flight time but decreased distance. • If the angle of release is low, the projectile has less flight time but increased distance* *However if the angle is too low, distance is poor.

  32. Angle of Release • How is distance and height manipulated in golf for the best shot? - Angle of club head.

  33. Speed of Release • Velocity (speed of motion) of release will determine the size of the flight path.

  34. Height of Release • The greater the height of release the greater the distance gained

  35. Spin • There are two main types of spin 1. Top spin- distance is decreased with topspin. 2. Back spin- distance is increased with backspin.

  36. Back Spin • A backspin shot creates a region of low pressure on top of the ball and a region of high pressure below. As a consequence, the ball floats suddenly thereby increasing the distance attained.

  37. Topspin Q. So how does Topspin work? A. A topspin shot creates a region of high pressure on top of the ball and a region of low pressure below. As a consequence, the ball dips suddenly thereby decreasing the distance attained

  38. A golf ball acquires spin when it is hit. Backspin is imparted for almost every shot due to the golf club's loft (i.e., angle between the clubface and a vertical plane). A spinning ball deforms the flow of air around it similar to an airplane wing; a back-spinning ball therefore experiences an upward force which makes it fly higher and longer than a ball without spin. The amount of backspin also influences the behavior of a ball when it impacts the ground. A ball with little backspin will usually roll out for a few yards/meters while a ball with more backspin may not roll at all, even backwards. Sidespin occurs when the clubface is not aligned perpendicularly to the plane of swing. Sidespin makes the ball curve left or right: a curve to the left is a draw, and to the right a fade (for right-handed players). Accomplished golfers purposely use sidespin to steer their ball around obstacles or towards the safe side of fairways and greens. But because it's sometimes difficult to control or predict the amount of sidespin, balls may take an undesirable trajectory, such as hook to the left, or slice to the right (for right-handed players).

  39. Stability & Balance

  40. Centre of Gravity • The point in the body about which all parts of the body are in balance or the point at which gravity is centred • COG is not confined to one location, as the body moves so the COG moves with it in the direction the movement occurs

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