# AS biomechanics

• Created by: wistuart
• Created on: 09-03-18 09:23
• AS Biomechanics
• Principles of biomechanics
• To analyze performance
• To refine and improve sporting technique
• To design new equipment to benefit athletes
• To prevent injuries of athletes
• Newton's laws
• 1.Inertia- A body will continue in a state or rest or constant velocity until an external force acts upon it.
• 2. Acceleration- The change in motion of a body is proportional to the force applied
• 3. Reaction- Every action has an equal and opposite reaction
• Equations
• Velocity= displacement/time taken (m/s)
• Momentum= velocity* mass (Kgm/s)
• Acceleration= (final velocity-initial velocity)/Time taken (m/s/s)
• Force= Mass* acceleration  (N)
• Weight= mass* acceleration due to gravity (10m/s/s)  (N)
• Net forces
• Net force= 0- This means that a body is in a state of constant velocity or a state of rest.
• Net force= 1- A body is accelerating
• A sum of all the forces acting upon a body
• Net force= -1- A body is decelerating
• Forces
• Vertical Forces
• Weight- The gravitational pull that the earth exerts on a body.
• Ground reaction force- The equal and opposite reaction to weight which is always present.
• Horizontal Forces
• Friction- The force that opposes the motion of two surfaces in motion.
• Factors affecting friction
• Roughness of the ground surface- increased roughness=  increased friction
• Athletes running on rough rubberized trackes instead of grass
• Roughness of the contact surface- Increased surface of contact surface= increased friction
• Athletes running with spikes instead of trainers
• Temperature- increased temperature of contact surface and surface= increased friction
• F1 drivers have a warm up lap
• Size of normal reaction- By increasing the  size of reaction friction is increased due to more force
• shot-putters have a bigger mass meaning they can throw harder and reduce over rotation
• Air resistance- The force that opposes the motion of a body travelling through the air
• Factors affecting air resistance
• Velocity- increased velocity= increased air resistance
• The faster a runner goes the more Air resistance they will have
• Shape- the more aerodynamic the shape= less air resistance
• Cyclists use a teardrop helmet as it is more streamline than a conventional helemt
• Frontal cross sectional area- decreased frontal cross sectional area= reduced air resistance
• The crouched position of skiers in straights
• Smoothness of surface- the smoother the surface the less air resistance
• The smooth lycra suits of sprinters
• Measured in newtons
• Analysis through technology
• Limb kinematics- 3d optical motion analysis- can be used to improve technique
• Force plates- measures ground reaction forces-focuses on power output-when an object makes contact the force plate produces an electrical output proportional to the force applies
• Wind tunnels- Used to develop drag reduction systems and used to see how aerodynamic an object is
• Centre of mass and stability
• Centre of mass- is the point at which the body is balanced from all points.
• stability is the ability of the body to reduce motion and stay at rest
• Factors affecting stability
• Mass of the body- The greater the mass of the body the greater the stability due to its increased inertia
• Prop forwards in rugby can withstand great applied forces
• Height of the Centre of mass- The lower the centre of mass the greater the stability
• When gymnasts land they bend their knees to avoid falling over
• Base of support- the greater the base of support the greater the stability
• When props move their feet further than shoulder width in a scrum
• line of gravity- the line that extends from the centre of mass downwards- more central the line of gravity to base of support the greater the stability
• A basketball player taking a free throw stands square
• Lever systems
• components of a lever; - lever (BONE) - Fulcrum (JOINT)   -Effort (Antagonist MUSCLE) -Load(WEIGHT OR Resistance)
• 1st class- Fulcrum in the middle
• Extension of the neck
• 2nd class- Load is in the middle
• Ball of the foot in take off phase of a jump