EDU4SBM Sports Biomechanics 1 Lecture Week 3 Force Production, Forces, COG, Inertia, Impulse

EDU4SBM Sports Biomechanics

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Lecture Week 3Lecture Week 3

Force Production, Force Production, Forces, COG, Inertia, Forces, COG, Inertia,

ImpulseImpulse


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Force ProductionA 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 objectChange the speed of a moving objectBalance another force to keep an object still


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Forces• Internal forces

• External forces


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Types of Forces

Force without motion – isometric force

Force with motion – isotonic force

Sub-maximal force

Maximal force


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Force without Motion• Isometric force • Isometric contraction• Muscle length does not change

Eg:


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

– Eg:


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Sub-maximal Force• Force needs to be at an optimal level for successful performance

• Sometimes we want less than maximum force

– Eg:


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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


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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


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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

Force Summation


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Simultaneous Force Summation


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Sequential Force Summation


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Sequential force summation requires the following techniques

1. Use as many body parts as possible

2. Use largest body parts and muscle groups first

3. Sequentially accelerate each body part

4. Sequentially stabilise each body part so the next body part accelerates around a stable base.


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


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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


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Inertia

A bodies resistance to change in its state of motion (either from rest or moving).

1. An objects resistance to beginning motion

2. 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


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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 = Ft measured in Newton Seconds.


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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.


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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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EDU4SBM Sports Biomechanics 1 Lecture Week 3 Force Production, Forces, COG, Inertia, Impulse