2.2 5 7 Biomechanics

7/30/2019 2.2 5 7 Biomechanics

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Joint Movement Agonist Antagonist

Knee

Hip

Trunk

Elbow



Biomechanics



Sections• Part 1: Newton’s Law of Motion

• Part 2: Force Summation• Part 3: Projectile Motion



Part 1: Newton’s Law of Motion

Law #1 An object at rest tends to remain at rest unless acted upon

by some external force, this is also known as INERTIA

Which of the following has the greater Inertia and why?

30kgs

20kgs

Answer: 30kg weight because it has a greater mass



Newton's first lawhttp://www.youtube.com/watch?v=BlFGN

2zlDYc

http://www.youtube.com/watch?v=BlFGN2zlDYc







Law #11.Basically inertia is an objects resistance to movement. Having

a great deal of inertia can be an advantage in some sports – Can

you think of three?

Of course having a lot of Inertia can have a disadvantage in some

sporting situations. How?

If you have a lot of Inertia you require a lot of force or effort to get moving.




Law #1

• The ball will keep

travelling untilgravity/air resistance

pulls it down or player

blocks the ball.




Law #22. When a force acts upon a mass, the result

is acceleration of that mass.

Consider the following three balls:

a) If each is hit with the same amount of force, which one

accelerates the most? Why?The table tennis ball – because it is lighter

b) If the tennis ball is hit with gradually increasing force, what

happens to its acceleration?

The acceleration will increase with increasing force




Law #2So considering this 2nd law we can say…

The greater the force, the greater the acceleration

The smaller the mass the greater the accelerationwhen a constant force is applied.

The mass will accelerate in the direction the force is

applied.

How could you apply Newton’s 2nd Law to a sporting situations



Newton's second lawhttp://www.youtube.com/watch?v=-

KxbIIw8hlc




Law #3

3. For every action, there is an equal and opposite

reaction.

a) When we apply a force to something, this is known as action force

b) The object we apply a force to, applies a force back a reaction force.

On the following pictures, draw in and label the two forces in action

actionreaction

actionreaction




Law #3

• The incoming ball is the

Action Force.

• Your body acts as a

reaction force.

• Because your body hasthe greater Inertia, the

ball is the reaction

reaction

action



Can you apply the 3rd law

to a jump in volleyball• Analyse this jump

serve.

• Where would you putthe necessaryarrows?

• Come draw on theboard

• What would happen if the ground had lessinertia than the

jumper?




Law #3

We can see pairs of forces working when we run

on sand. We run forward and sand is kicked up

behind us in the opposite direction.

What other example of this can you think of?

When a ball is bounced, it bounces back

in a direction opposite to that in which it

was dropped



Newton's third law



Part 2: Force Summation• Many of the skillsperformed in sport requiremaximum speed or force tobe generated.

Eg throwing a ball, rowing askiff

• In order to do this, an

athlete needs to involve asmany body parts aspossible, moving them inthe correct order.



Part 2: Force Summation• Think about when you throw

a discus during athletics.

• List the body parts you used

in the order you used them

• The more body segments

involved, the greater the

force or speed generated.



Part 2: Force Summation

• Think about throwing

a Javelin. List theorder you use your

body parts when you

throw the javelin.

Legs, hips, trunk, shoulder, elbow, wrist




sequence• If you wish to achieve

maximum velocity, it isimportant that each bodypart is used in the correctsequence.

• You use the strongest,heaviest muscles first,before using the smaller,faster muscles last -Thisovercomes inertia




Timing• The timing of the application of the

forces is vital

• A body part should begin to movewhen the previous body part isexerting maximum force / speed

• Example: In a well-timed Volleyballspike; the forearm begins to extendat the elbow just as the upper armbegins to decelerate



Force Summation

Experiment

• In pairs get a medicine ball andmeasure the required throws.

• Identify which one result was thelongest and explain why.

• Hand sheet back in with both nameson it



Part 3: Projectile Motion• Any body released into the air

is a projectile. This meansthat once it is in the air it has

no extra propulsion.

• A body can be released intothe air by either:

- Throwing – Discus

- Striking – Tennis

- Projecting the body

itself- High jump



Part 3: Projectile Motion

TRAJECTORY (path of a projectile)

Propelling factors

- Speed of release

- Height of release

- Angle of release

Factors in the air

- Gravity

- Air resistance



Part 3: Projectile Motion TRAJECTORY (path of a projectile)

Speed of release

- The greater the speed

of release, the greater the horizontal distance

Height of release

- The greater the height of release, the greater the

horizontal distance

In Volleyball, what advantage is there in a jump serve?




Angle of release

- There is an optimum

angle of release for each object, but that will

depend on a number of

factors including

aerodynamics of theobject and height of

release.




There are several key factors that we mustconsider:

- MASS: The smaller the mass (lighter), the moreair resistance will affect it.

- SURFACE: If the surface is rough and largethen air resistance will be greater.

- SPEED: As speed increases so does air resistance.

Air Resistance

Air resistance acts on the horizontal component of the projectiles path.



Part 3: Projectile Motion TRAJECTORY (path

of a projectile)

Look at the following video.

Identify and explain all

factors of projectile motion

that have been covered.

-Speed of release

-Height of release

-Angle of release

-Gravity

-Air resistance

http://www.youtube.com/watch?v=WlRb4UvO20M

2.2 5 7 Biomechanics

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