biomechanics

newtons 1st law

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

newtons 2nd law

the rate of momentum experienced by the object is proportional to the size of the force and takes lace in the direction which the force acts

newtons 3rd law

every action has an equal and opposite reaction

types of motion

linear motion, angular motion, general motion

linear motion

movement of a body in a straight or curved line where all parts are moving the same distance in the same direction over the same time

example of linear motion

100m sprint/swim

what newtons law relates to linear motion

newtons 1st law

angular motion

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

what newtons law relates to angular motion

newtons 1st law

example of angular motion

shoulder during cricket bowl

what causes linear motion

direct force applied to the body through the COM

what causes angular motion

eccentric force applied to a body outside of the COM

general motion

it is a combination of linear and angular motion

example of general motion

swimming, running, cycling

explantion of general motion

the trunk moves in linear motion and as a result of other body parts moving in angular motion and shoulder and hip joint

velocity

the rate of change in displacement

units of velocity

m/s

equation for velocity

velocity=displacement/time

momentum

the quanity of motion possessed by a moving body

units of momentum

kgm/s

equation of momentum

momentum= mass X velocity

acceleration

the rate of change of velocity

units of acceleration

m/s/s

equation of acceleration

(finial velocity-initial velocity)/time taken

5 ways to increase acceleartion

1. increase force/velocity/speed

2. increase friction

3. reduce mass/weight

4. improve technique

5. decrease air resistance

centre of mass

the point where all the mass of the body tends to be concentrated and balanced in all directions

what does COM depend on?

1. body position

2. athlete body shape

3. gender

stability

a stable body position will enable an athlete to resist motion

line of gravity

an imaginary line which extends from the centre of mass directly to the ground

how do you increase stability?

1. increase mass of body

2. increase size of base support

3. lower COM

4. increase number of contact points

5. bring line of gravity inside the base support

force

a push or pull that alters the state of motion of a body

force units

newtons

equation for force

force= mass x acceleration

net force

the overall force acting on a body when all individual forces have been considered

vertical forces

weight and reaction force

horizontal force

friction and air resistance

weight

gravitational force that the Earth exacts on a body

reaction force

whenever there is a point of contact between two bodies there will alway be this force

air resistance

the force that opposes motion of a body travelling through air

friction

the force that opposes the motion of two surfaces in contact

types of friction

sliding friction, direction friction, parallel friction

sliding friction

occurs when two surfaces have a tendency to slide over one another

direction of friction

acts in the opposite direction to motion

parallel friction

acts parallel to the two surfaces in contact with eachother

factors affecting friction

1. roughness of footwear/object

2. roughness of ground

3. size of down force

4. temperature of surface

factors affecting air resistance

1. shape of object

2. velocity

3. frontal cross sectional area

4. smoothness of surface

how to increase acceleration

1. technique

2. footwork

3. conditions

4. body shape

how to increase deceleration

1. force

2. air resitsance

3. body shape

what is a load arm

the perpendicular distance from the fulcrum to the load

what is the effort arm

the perpendicular distance from the fulcrum to the effort

what is a 1st class lever

fulcrum in the middle

what is a 2nd class lever

load in the middle

what is a 3rd class lever

effort in the middle

example of 1st class lever

header (fulcrum= joint between atlas and skull, load= weight of head, effort= trapezius )

example of 2nd class lever

pirouette in ballet (fulcrum= joint between phalanges and metatarsals, load= weight of body, effort= plantarflexion)

example of a 3rd class lever

bicep curl (fulcrum= elbow, load= weight, effort= biceps brachii)

which lever has mechanical advantage

2nd class

what is mechanical advantage

ability to move large load with small effort, larger effort arm than load arm

what lever has mechanical disadvantage

3rd class lever

what is mechanical disadvanatge

lever struggles with heavy load, load arm is longer than the effort arm

what is limb kinematics

the study of motion, limbs and movement through video, 3D analysis.

what is a strength of limb kinematics

improve technique, improve posture, helps with injury rehabilitation

what is a weakness of limb kinematics

accessibility, cost, requires specialist data to interpret

what are force plates

rectangular metal plates in the ground that measure force

what is a strength of force plates

to design prothesistics, to improve technique, rehabilitation

what is a weakness of force plates

expensive, requires specialist training, must be calibrated

what are wind tunnels

they are used to stimulate air resistance

what are postives of wind tunnels

improve technique (aerodynamic), to test equipment design

what are weaknesses of wind tunnels

accessibility, cost, training to interpret data

what are the key factors of linear motion

distance, displacement, speed, velocity, acceleration

what is distance

total length from start to finish (m)

what is displacement

the shortest straight line route from start to finish (m)

what is speed

the rate of change in distance (m/s)

what is velocity

the rate of change in displacement (m/s)

what is acceleration

the rate of change in velocity (m/s/s)

what are the graphs of linear motion

distance/time graphs, speed/time graphs, velocity/time graph

what is torque

a turning force- the greater the eccentric force, the greater the angular motion

what are the 3 axis of rotation

1. longitudinal (from head to toe)

2. transverse (from side to side)

3. frontal (from front to back)

what is angular motion measured in

radians (rad/s)

what is angular velocity

the rate of change in angular displacement

what is the equation for angular velocity

AV (rad/s)= angular displacement (rad)/time (s)

what is moment of inertia

the resistance if a body to change its state of angular motion

what is the equation for moment of inertia

MI (kgm2)= mass(kg) x distribution of mass from axis of rotation (m2)

what 2 factors affect MI

mass

distribution of mass from the axis of rotation

mass (moment of inertia)

the greater the mass, the greater the moment of inertia, decreases angular velocity

distribution of mass (moment of inertia)

close mass distribution from axis, decrease moment of inertia, increase angular velocity

what is angular momentum

the quantity of angular motion possessed by a body

what is the equation foo angular momentum

AM= MI x AV

conservation of angular momentum

AM is constant. As MI increases, AV decreases

what can affect drag and air resistance

1. velocity (greater velocity= greater drag and AR)

2. frontal cross-sectional area (larger= greater drag and AR)

3. shape (more streamlined= less drag and AR)

4. surface characteristics (smooth surface= less drag and AR)

what is projectile motion

movement of a body through air flowing a curved flight path under the force of gravity

what 4 things can imapct projectile motion

1. speed of release

2. angle of release

3. height of release

4. aerodynamics

how does the speed of release impact projectile motion

the greater force applied to projectile, greater acceleration, so travels further

how does the angle of release impact projectile motion

45- optimal angles= greatest distance

less than 45- not enough height

what is a parabolic flight path

a uniform curve, symmetrical about its highest point, unaffected by air resistance caused by a dominant weight force

what is a non parabolic flight path

asymmetric about its highest point caused by the dominant force of air resistance on the projectile

what is Bernoulli’s principle

the higher the velocity of air flows the lower the surrounding pressure

what is Bernoulli principle (explanation)

aerofoil shape causes air to travel a greater distance with a greater velocity so low pressure above, air travels a shorter distance so lower velocity so high pressure below, air moves from high to low pressure down the pressure gradient so creates a lift force