Transcript Biomechanics

Biomechanics
Newton’s Laws of Motion
• There are three laws that you need to be able to
apply to volleyball.
Newton’s 1st Law – The Law of
Inertia
• “ A body continues in its state of rest or uniform
motion unless an unbalanced force acts upon it”
• Basically once something is at rest or begins moving it
will keep doing so until acted upon by another force.
• Inertia – is a body’s tendency to remain at rest or in
motion. The more mass an object has the larger its
inertia.
Example
• When performing a chest pass,
unless a player applies a force
through the hands to pass the
ball, the ball will sit in the
players’ hand, remaining at rest.
Your turn
• Write below/alongside how you could apply Newton’s
1st Law to a Volleyball Skill. SET
Newton’s 2nd Law – The Law of
Acceleration
• “the acceleration of an object is directly
proportional to the force causing it, is in the
same direction as that force, and is inversely
proportional to the mass of the object.”
• Bigger force = bigger acceleration.
• Smaller mass = bigger acceleration.
• Force = mass X acceleration
Example
• If a person hit a golf ball and
a cricket ball with a cricket
bat, the golf ball will
accelerate quicker because it
has less mass.
• The ball will accelerate
quicker when hit with a large
amount of force (front foot
drive) than with a less
forceful stroke (forward
defensive)
Your turn
• Write below/alongside how you could apply Newton’s
2nd Law to a Volleyball Skill. SERVE
Newton’s 3rd Law – The law of
reaction
• “For every action there is an equal and opposite
reaction”
• Whenever a force is applied to something there
will be an equal and opposite force going in
the other direction.
• Medicine ball throw sitting on a Swiss ball
Example
• When a sprinter pushes off the
blocks, he applies a force by
driving his foot into the block –
there is an equal and opposite
reaction of his body being
propelled away from the blocks.
• By driving his foot into the
blocks the sprinter is using
ground reaction forces to propel
his body.
Your turn
• Write below how you could apply Newton’s 3rd Law to
a Volleyball Skill. BLOCK
LEVERS - First Class Lever
• E.g Head on Vertebrae
Resistance
• Fulcrum in Middle
Fulcrum
Effort
Second Class Lever
Resistance
Fulcrum
Effort • E.g Rising on to toes /
calf raise
• Resistance in the
Middle
Third Class Lever
• E.g Bicep Curl
Effort
Fulcrum
Resistance
• Effort in the Middle
• Most
frequently
occurring lever
in the body
Maximising lever length to improve
performance.
• Shortening the lever arm (by bending the joint)
allows the lever arm to generate force and to be
rotated with more speed.
• Once this is has been achieved the lever arm can
be lengthened (by straightening the joint to
maximise the speed at the end of the lever.
• This can be used to strike and propel objects
more effectively.
Example
• The player reduces the lever arm length by flexing their elbow,
allowing force to be generated and the racket swung with more
speed. As the ball is hit, the elbow extends to increase the length
of the lever and allow the racket head to travel at full speed. This
allows the ball to leave the racket head with more speed.
• Fulcrum = shoulder, Force = anterior deltoid, Resistance =
racket head
Your turn
• Write below how you could maximise lever length to
improve a Volleyball Skill. SPIKE
Momentum
• The amount of motion an object has. It is a
combination of mass and velocity.
• Momentum = Mass X Velocity
• Transfer of momentum can occur internally or
externally
Example
• Forearm pass in volleyball
• Small downward momentum
applied by the ball.
• Large upward momentum
applied by the forearm.
• Resulting momentum applied
to the ball – in the direction
of the largest force.
Force Summation
• Allows maximum forces to be produced by the
muscles and then transferred into the physical
activity.
• Achieved by adding forces of each body
segment together. Therefore producing a larger
force than one force alone.
Relationship between number of body parts used and force
produced
LARGE FORCE
Hand
SMALL FORCE
Shoulder/arm
force
Hand
Trunk
Shoulder/
arm
Hip/thigh
time
Maximising force summation
• Begin movements with the larger muscles of the body.
• Once the larger muscles have been recruited, force can
be transferred through to the smaller muscles of the
extremities (hand and feet)
• Correct timing allows maximum transfer of force
between body parts. If a certain body segment begins
to accelerate before or after the previous segment has
reached peak force, less force will be transferred.
Your turn
• Write below how you maximise force summation to
improve a volleyball skill. SERVE
Projectile Motion
• Any object released into the air is termed a
projectile.
• The flight of a projectile consists of a horizontal
and vertical component.
Vertical
component
Horizontal component
Factors affecting the flight of a
projectile:
1.
2.
3.
4.
5.
6.
Gravity
Air resistance
Speed of release
Angle of release
Height of release
Spin
Gravity
• Gravity acts upon a body to give it mass.
• The greater the weight of an object the greater
the influence of gravity upon it.
• Gravity limits the height that a projectile can
attain. (acts on the vertical component of flight)
Air resistance
•
1.
2.
3.
4.
In many sporting activities, the effect of air resistance
is very small, but several factors influence it:
The larger the surface to volume ratio the more air
resistance. Shuttlecock – golf ball.
The surface of the object. If it is rough then air
resistance will be greater.
Speed – as speed increases so does air resistance.
Mass – the lighter the object the more air resistance
will affect it.
Speed of release
• Generally the greater the speed of release the greater the
distance gained.
• Speed of release is divided into two components:
Vertical component
• a) initial vertical velocity
Direction of flight
• b) initial horizontal velocity
Horizontal component
Angle of release
• For any given speed of release, the optimum
angle of release is 45°. This assumes that there is
no air resistance, and that the landing point and
take off point are at the same height.
• IN most sporting situations the angle of release
is usually around 35° to 45°. This is due to air
resistance and the take off point is normally
higher than the landing point.
Height of release
• For a given speed and angle of release, the
greater the height of release the greater the
distance gained.
• This is due to having more time in the air.
• Eg. A golfer hitting a ball off the top of a hill
would hit it further than a golfer at the bottom
of the hill.
Spin
• Two basic principles are:
1. Range is decreased with topspin
2. Range in increased with back spin
low
high
Direction
of ball
Direction
of ball
high
low
TOPSPIN
BACKSPIN
Spin
• The reason a ball with topspin dips suddenly
and a backspin shot will travel further is due to
air pressure.
• Topspin high pressure on top of the ball forcing
it down
• Backspin high pressure under the ball forcing it
up.
Your turn
• How could use of projectile motion be used to improve a volleyball serve that
goes into the net all the time?