biomechanical principles and levers Flashcards
linear motion definition
motion in a straight or curved line where all body parts move in same distance, speed and direction
explanation of newtons first law
law of inertia-force is required to change state of motion
if object at rest will remain still
if moving in one direction will continue at same velocity until force is exerted upon it
bigger the mass, harder it is to overcome inertia as more force needed to change state of motion
e.g. sumo wrestler
makes bigger impact when inertia is overcome as the large mass makes a bigger fall
inertia definition
resistance an object has to a change in its state of motion
newtons second law of motion
law of acceleration
magnitude (size) and direction of force determines magnitude and direction of acceleration
rate of acceleration is directly proportional to force causing change
mass remains constant, then acceleration is equal to force causing it
runner must have large force to allow themselve to accelerate
equation to work out the size of a force
force=mass x acceleration
newtons third law
law of reaction
for every action (force)there is an equal and opposite reaction (force)
describes what happens when two bodies exert forces on one another
action acts on one body, reaction acts on the other body
sport example of law of reaction
runner pushes down on starting blocks (action)
blocks push forward on the athlete (reaction)
many questions of law of reaction mention GRF (ground reaction force)
Ground reaction force (GRF) definition
force exerted on the ground by the body in contact with it
sport example of 1st law
penalty
ball remains still (state of rest) until force exerted upon it (kicked by player)
sport example of 2nd law
when player kicks ball, acceleration of the ball is equal to size of the force
sport example of 3rd law
header
when football jumps up (action)
force exerted on ground to gain height
same time, ground exerts an upward force (equal and opposite) upon the player
scalar quantity definition
when measurements are described in terms of just their magnitude and size
DIRECTION NOT TAKEN INTO ACCOUNT
speed definition
rate of change of position
speed equation
distance covered (m) divided by time taken (s)
distance
length of the path a body follows when moving from one position to another
distance calculation
distance=speed x time
centre of mass
point of balance
body constantly moving, so centre of mass constantly changing
body irregular shape so hard to identify centre of mass
factors affecting stability
height of centre of mass-lowering centre of mass increases stability
position of line of gravity-should be central over base of support to increase stability
area of support base-more contact points, larger base of support, increase in stability e.g headstand more balanced then handstand as has more contact points so more stability
mass of the performer-greater mass, more stability as increased inertia
what are the 3 components of a lever
EFL THE ELF FEL
bones-levers
effort-muscles
fulcrum-joint
load-weight of body part being moved
first class lever
EFL
where the fulcrum (joint) is located between the effort(muscles) and the resistance(body part)
movement in first class lever
movement of head and neck during flexion and extension
extension of elbow
second class lever
ELF
this is where the load is located between both the effort and the fulcrum
movement in second class lever
plantarflexion in ankle only
third class lever
FEL
this is where the effort is located between the fulcrum and load
movement in third class lever
hip knee and elbow flexion
mechanical advantage
where force arm is longer then resistance arm
means lever system can move large load but over short distance and requires little force
mechanical disadvantage
reisistance arm is longer then force arm
cannot lift as heavy but faster
what is the force arm
shortest distance between fulcrum and effort
what is the resistance arm
shorted distance between fulcrum and resistance
