Biomechanical principles, levers and the use of technology

Newton's laws of motion
First law: Law of intertia

A body continues in a state of rest or uniform velocity unless acted upon by an external force

Golf ball will remain still unless the force applied by a golf club makes it move, or a golf ball will continue to move at a constant velocity unless a force a

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Newton's laws of motion
Second law: Law of acceleration

Body's rate of change of momentum is proportional to the size of the force applied and acts in the same direction as the force is applied

When a golf ball is struck the rate of change in momentum is proportional to the size of force acted upon it. Bigger

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Newton's laws of motion
Third law: Law of reaction

Every action has an equal and opposite reaction

If a tennis player hits a ball the racquet exerts a force on the ball and the ball exerts an equal and opposite force on the racquet

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Velocity (m/s)

Rate of change of displacement
Velocity = Displacement/time taken

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Momentum (kg m/s)

Quantity of motion possessed by a moving body
Momentum = Mass*Velocity

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Acceleration (m/s/s)

Rate of change of velocity
Acceleration = (final velocity-initial velocity)/time taken

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Force (N)

Push or pull that alters state of motion of a body
Force = Mass*Acceleration

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External forces
Vertical forces

Weight - Gravitational pull that the earth exerts on a body. Measured in newtons and calculated by mass*acceleration.
Reaction - Force exerted by a body in response to action force placed upon it. Measured in newtons and a result of Newton's third law

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External forces
Horizontal forces

Friction - Force opposing motion of two surfaces in contact. Affected by 4 factors; roughness of each surface (2), temperature and size of reaction
Air resistance - Force opposing motion through the air. Affected by 4 factors; velocity, shape, frontal cro

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Centre of mass

Point at which an object or body is balanced in all directions. Point where weight of body tends to be concentrated

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Factors affecting stability

Mass of the body - Larger mass - Larger stability
Height of the centre of mass - Lower centre of mass = Larger stability
Size of base of support - Greater size of support = Larger stability
Line of gravity - More central line = Larger stability

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Levers

Component - Location - Example: Upward phase of bicep curl
Lever - Bone - Line - Radius and ulna
Fulcrum - Joint - Triangle - Elbow joint
Effort - Muscle force - Arrow - Force by bicep brachii
Load - Weight/Resistance - Arrow - Weight of forearm and free

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Limb kinematics

Definition - Study of movement in relation to speed and time
Use - 3D optical motion analysis records athlete to understand the efficiency of the movement
Optimising performance - Data can be used to improve performance or technique

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Force plates

Definition - Ground reaction forces measured in lab conditions
Use - Balance, run and jump on a plate assessing size and direction of forces
Optimising performance - Used for sport biomechanics, therapy and balance rehab

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Wind tunnels

Definition - Steel frame containing wide fans where artificial wind is produced
Use - To develop drag reduction system
Optimising performance - Study the flow of air around the object, aim to improve the flow of air around an object

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Biomechanical principles, levers and the use of technology

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