# Biomechanics.

## Presentation on theme: "Biomechanics."— Presentation transcript:

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 Fulcrum in Middle Resistance Fulcrum Effort

Second Class Lever Effort E.g Rising on to toes / calf raise
Resistance in the Middle Resistance Fulcrum

Third Class Lever Most frequently occurring lever in the body
E.g Bicep Curl Effort in the Middle Most frequently occurring lever in the body Effort Resistance Fulcrum

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:
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 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: a) initial vertical velocity b) initial horizontal velocity Vertical component Direction of flight 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: Range is decreased with topspin
Range in increased with back spin low high Direction of ball Direction of ball high low BACKSPIN TOPSPIN

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?