# Biomechanics

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Biomechanics

Definition: Sport science that uses mathematics and Newtons Laws of motion to explain movement. It can help a coach to optimise an individuals performance and adjust technique.

Biomechanics is covers two aspects of motions, Linear and Angular.

Linear motion- Movement of an object in a straight line when force is applied through centre mass. Example- Hitting a snooker ball in the centre of the ball in a straight line is an example of Linear motion.

Angluar motion- Movement of a rotating object when force is applied off centre. This force can be described as excentric force. Example- Hitting a golf ball at the base, so applying excentric force, causing Angular motion.

Newton's 3 Laws of Motion:

• The first Law of motion (N1)- The law of Inertia: An object will remain in a state of inertia (state of constant (motion/no motion)). Application- The gold ball will remain stationary on the tee until a force is applied that is enough to overcome Inertia
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• The second Law of motion (N2)- The law of Acceleration: The greater the force applied to an object, the greater the rate of acceleration in the direction of which the force is applied. Application- To reach the hole, the golfer will have to apply enough force to reach the green in a straight line.
• The third Law of motion (N3)- The law of Reaction: For every action, there is an equal and opposite reaction. Application- A sprinter will apply force to the starting blocks (e.g 100N), and the starting blocks will apply the same force back (100N).

Fluid mechanics:

Definition: The study of forces and flow within fluids (gas and liquid).

This branch of biomechanics is concerned with any sport that includes flight or movement through water, for example tennis and swimming. Tennis- the flight of the ball after force is applied by the racquet. Swimming- the movement of the swimmer through the water.

The Bernoulli principle:

• A concept that uses fluid dynamics to explain why projectiles can remain in flight. The principle is that as velocity increases, pressure decreases causing a lift force.
• This means that the air flowing over the top of a wing travels faster than air travelling under the wing, as it has further to travel. This reduces the pressure above the wing, while maintaining a lower pressure under the wing, which is what allows planes to remain in flight.
FAST FLOW, PRESSURE LOW
• Practical application: Ski jumpers lean as far forward as they can to increase the distance which air has to travel over the skis, which again reduces the pressure. The pressure differential between above and below the ski causes lift.
• The Magnus Effect:

This is effectively the Bernoulli principle applied to spinning objects. This considers how the effect of a fluid flowing around an object creates spin.

• When a spinning object moves through the air, a 'boundary' layer of molecules moving in the same direction is formed.
• This boundary layer comes into contact with the opposing air flow,