biomechanics

newtons first law (inertia)

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

newtons second law (acceleration)

the momentum of a force applied to an object is proportional to the size and direction of the force applied to it

newtons third law (reaction)

for every action force there is an equal and opposite reaction

velocity

the rate of change of displacement

velocity equation

displacement/time taken (m/s)

momentum

the amount of motion a body possesses

momentum equation

mass x velocity (kg m/s)

acceleration

the rate of change in velocity

acceleration equation

(final velocity - initial velocity) / time taken (m/s2)

force

a push or pull

force equation

mass x acceleration (N)

5 effects of force

accelerate, decelerate, cause resting body to move, cause moving body to stop, cause body to change shape/direction

net force

the sum of all forces acting on a body (resultant force)

balanced forces

occurs when 2 or more forces acting in opposite directions are equal in size

weight

the force exerted on an object due to gravity (N)

friction

2 surfaces in contact moving in opposite directions

4 impacts on friction

surface roughness, contact surface roughness, temperature, size of reaction force

air resistance

the force acting opposite to the relative motion of an object moving through the air.

4 impacts on air resistance

velocity, streamline, frontal cross-sectional area, surface characteristics

centre of mass

the point at which the body's mass is equally distributed in all directions

first class lever

load, fulcrum, effort (flexion of elbow during upwards phase of bicep curl)

second class lever

effort, load, fulcrum (gymnast creating plantar flextion at ankle by pointing toes during handstand)

third class lever

fulcrum, effort, load (extension at the elbow during downwards phase of bicep curl)

mechanical advantage

effort arm longer than resistance arm (downwards phase of bicep curl)

mechanical disadvantage

load arm longer than effort arm (tennis player looking at ball during serve)

limb kinematics

study of movement in relation to time and space e.g. 3D recordng of athlete performing sporting action, evaluates limb efficiency in motion, measures angles within performer’s technique and movement, uses infrared cameras collecting data through red dots linked to computer, analyses whole body/limb movements + how to prevent an injury, BAD = expensive/requires specialist/hard to access

force plates

rectangular plate built into the ground with built in force transducers, electrical impulse that is proportional to the force applied is displayed graphically on computer when contact is made with plate, measures gait/balance/force/acceleration/ velocity/time, GOOD = instant and reliable results, optimise angle of take off, injury prevention, BAD = expensive, requires specialist

wind tunnels

measure aerodynamic efficiency, engineers study flow of air around body, GOOD = lots of data to improve, immediate data, BAD = expensive, requires specialist

linear motion

motion in a straight or curved line with all the body parts moving in the same distance at the same speed in the same direction

angular motion

movement of a body or part of a body in a circular path about an axis of rotation

eccentric force/torque

a force whose line of motion does not pass through the body’s centre of mass

moment of inertia

resistance of a body to change its state of angular motion

moment of inertia equation

sum of mass x redistribution of mass from axis of rotation2 (sumM x r2)

angular velocity

rate of change in angular displacement OR rate of rotations (radians/s)

angular momentum equation

moment of inertia x angular velocity

newtons first law (angular)

a rotating body will continue to turn about its axis of rotation with constant angular momentum unless an eccentric force is exerted upon it

newtons second law (angular)

the rate of change of angular momentum of a body is proportional to the force causing it and the change that takes place in the direction

4 factors that impact drag in water

frontal cross-sectional area, streamline/shape, surface characteristics, velocity

velocity of moving body

greater velocity = greater AR/drag

frontal cross-sectional area of moving body

larger the frontal cross-sectional area = greater AR/drag

streamline/shape of moving body

streamlined shape (e.g. aerofoil/tear drop) = less AR/drag

surface characteristics of moving body

smoother surface = lower AR/drag

3 factors affecting projectile motion

height of release, speed of release, angle of release

height of release

if release height is greater than landing height (positive relative release height), the optimum angle of release = 45 degrees. if release height is lower than landing height (negative relative release height), the optimum angle of release is more than 45 degrees

speed of release

greater relase speed = greater horizontal displacement

angle of release

release height and landing height equal = 45 degrees, release height greater than landing height = less than 45, landing height greater than release height = more than 45

Bernoulli principle

if additional lift force is created then the projectile will increase flight time, flight path and horizontal displacement of projectile

slice

right

hook

left