Biomechanical Principles

• Newton's first law is the Law of Inertia.
• The Law of Inertia states A body continues in a state of rest or of uniform velocity unless acted upon by an external unbalanced force.
• Newton's second law is the Law of Acceleration.
• The Law of Acceleration state A body's rate of change in acceleration or momentum is directly proportional to the size of the force applied and acts in the same direction as the force applied.
• Newton's third law is the Law of Reaction.
• The Law of Reaction states for every action force applied to a body there is an equal and opposite reaction force.
• Newton's first law can be seen in the sprint start as the runner is at rest in the blocks until the blocks provide a force to cause her to overcome inertia and start accelerating.
• Newton's second law can be seen in the sprint start as the sprinter's acceleration is directly proportional to the amount of force provided by the blocks and in the same direction.
• Newton's third law can be seen in the sprint start as the sprinter applies a force to the blocks, and the block apply an equal and opposite force back to the sprinter.
• The role of the centre of mass is crucial to sports performance.
• The centre of mass is the point at which the body is balanced and weight is equally distributed.
• In the human body, the centre of mass is not a fixed point located in a specific part of the body.
• The centre of mass' location will vary depending on the body position.
• The centre of mass can also fall outside the body.
• The centre of mass follows a predetermined flight path.
• We can move the centre off mass around and outside the body to enhance sporting performance.
• In the Fosbury flop, the high jumper raises their knee and arms to raise the C of M prior to take off.
• During the Fosbury Flop flight, the performer will extend their spin and flex their knees. This moves the C of M outside of the body and below the bar.
• The Fosbury Flop technique allows higher heights to be achieved with the same force as previous techniques.
• The more stable you are the more you can resist knocks and intimidation through contact sports.
• Sometimes it is beneficial to be unstable , like a badminton player wanting to change direction or a gymnast performing sommersault.
• There are 4 factors that affect a sportsperson's stability: the position of the centre of mass; position of the line of gravity; base of support; and mass of the athlete.
• The lower the COM the more stable the performer.
• The higher the COM the less stable the performer.
• The line of gravity needs to be over the base of support for increased stability.
• If the line of gravity is not over the base of support the athlete will be unstable.
• The more contact points you have with the ground and the larger the base of support, the more stable you will be.
• Mass can increase stability as it takes more force to move (this is due to inertia).
• A force is a push ot pull that alters a state of motion.
• Motion is another term for the movement of a body.
• For there to be a change in motion a force must be applied. The greater the force the sprinter applies the greater the acceleration.
• When all forces are considered the resultant force acting on a body is termed net force.
• If there is a net force present the body will be changing its state in motion.
• If net force is zero there is no change in motion.
• Balanced forces occur when two or more forces acting on a body are equal in size and opposing in direction.
• With balanced forces the net force is zero, and the body will remain at rest or in morion at constant speed or uniform velocity.
• Unbalanced forces these occur when two forces are unequal in size and opposing direction.
• A net force will be present with unbalanced forces and the body will change its state of motion, either accelerating (positive net force) or decelerating (negative net force).
• Weight is the gravitational pull that the earth exerts on a body.
• Weight acts directly downwards.