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Lecture Week 3 Force Production, Forces, COG, Inertia, Impulse

Lecture Week 3 Force Production, Forces, COG, Inertia, Impulse. Force Production A force is a push or pull that changes, or tends to change the shape or the state of motion of an athlete or object. Force can: Change the direction of a moving object Change the speed of a moving object

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Lecture Week 3 Force Production, Forces, COG, Inertia, Impulse

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  1. Lecture Week 3 Force Production, Forces, COG, Inertia, Impulse

  2. Force Production A force is a push or pull that changes, or tends to change the shape or the state of motion of an athlete or object • Force can: • Change the direction of a moving object • Change the speed of a moving object • Balance another force to keep an object still

  3. Forces • Internal forces • External forces

  4. Types of Forces Force without motion – isometric force Force with motion – isotonic force Sub-maximal force Maximal force

  5. Force without Motion • Isometric force • Isometric contraction • Muscle length does not change Eg:

  6. Force with Motion • Isotonic force • Isotonic contraction • Muscle length changes • Changes the state of motion of the object (body) • Eg:

  7. Sub-maximal Force • Force needs to be at an optimal level for successful performance • Sometimes we want less than maximum force • Eg:

  8. Maximal Force • Some activities require maximal force for a higher chance of success • This usually happens through combination of a number of forces – force summation

  9. Force Vectors Vector - means a quantity has direction Force vector - indicates the magnitude and direction of an applied force. Every force vector has a horizontal and vertical component

  10. Force Summation Combination of forces to produce a maximal force 2 types • Simultaneously: • Eg: high jump take-off, vertical jump for rebound in basketball • Sequentially: • Eg: throwing, striking, kicking

  11. Simultaneous Force Summation

  12. Sequential Force Summation

  13. Sequential force summation requires the following techniques • Use as many body parts as possible • Use largest body parts and muscle groups first • Sequentially accelerate each body part • Sequentially stabilise each body part so the next body part accelerates around a stable base.

  14. Write down the steps in force summation for a throw from the outfield in softball.

  15. Centre of Gravity Single segmental objects have their Centre of Gravity directly above the base of support. Sometimes the Centre of Gravity can be found outside the body. (Arc) The balance point of an object

  16. Inertia • A bodies resistance to change in its state of motion • (either from rest or moving). • An objects resistance to beginning motion • An objects resistance to changing its state of motion • The heavier the object the greater its inertia and • therefore the greater force required to move it. • Inertia α Mass

  17. Impulse When a force is applied to an object, the product of the force (F) and the length of time (t) that the force is applied, is called the impulse of the force. Impulse = Ftmeasured in Newton Seconds.

  18. The Follow Through in Sport In racket and bat sports, hitters are often encouraged to follow-through when striking a ball. Following through increases the time over which a collision occurs therefore increasing the impulse This contributes to an increase in the velocity change of the ball. By following through, a hitter can hit the ball in such a way that it leaves the bat or racket with more velocity (i.e., the ball is moving faster). In tennis, baseball, racket ball, etc., giving the ball a high velocity often leads to greater success.

  19. Homework Task Answer the following questions 1. Pick one benefit of biomechanics for a sport of your choice and discuss in detail 2. For the same sport analyse and discuss in detail one form of equipment that has used biomechanics 3. Describe the sequence of body parts in the force summation for a tennis serve

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