Biomechanic for movement

Rotation occurs when all the parts of the body move through the same angle, in the same direction at the same time.

the central line through point of rotation. it is perpendicular to the plane of rotary motion. internal or external

change in angular postition (theta). vector quantity, +ve anticlockwise, -ve is clockwise.

(theta) angular position of a body relative to zero

(w)= change in theta(angular displacement) / change in time

zero

change in angular velocity (w) / change in time and it is a vector quantity

They are measured from the right hand horizontal or the vertical to the segment of interest.

angles between segments. possible both segments are moving

for a rigid body moving about a fixed axis with constant acceleration

the motion of any point on a rotating body can be described in linear terms. the linear variable for a particular point on a rotating body are related to the angular variables for that body

v =( r ) x (w)
w is in radians per second

if an object is rotating in a circle there is always an acceleration to the centre of the circle. represents change in angular motion. also known as radial acceleration

if an object is rotating in a circle there is always an acceleration along the path of angular motion. theis is the represention of change in linear velocity. perpendicular to centripetal acceleration.

a force whose line of action passes through the center of gravity (COG) of the body on which it acts causing rotation.

a turning or rotary force also known a moment. is in Nm

perpendicular distance from the force line of action to the axis of rotation.

-muscle length at the joint angle and its ability to contract/ generate force

-as joint angle changes the angle of attachment of muscles change, therefor perpendicular distance to joint changes
-the longest moment arm is when angle of attachment to bone is 90 degrees

rotary act at 90 degrees to the segment and provide force to rotate/move the lever.
translatory act parallel to the segment

a rigid structure that is hinged at one point and has forces applied at another 2 points. a hinge is a pivot point that is the fulcrum. resistance opposes movement and force causes movement.

to increase the effect produced when a force is exerted. it can also increase the speed at which a body can be moved.

depend on the length of the lever arm. If force lever is the longest then it increase force effect. if the resistance lever arm is the longest than it increases the speed.

ratio of the length of the force arm to the length of the resistance arm. FA/RA

if it equal one than FA=RA and its balanced (scissors)
if it is greater than one FA>RA and its a force advantage (wheel barrow)
if it is less than one RA>FA and is a speed advantage (call and bat)

fulcrum located between the force and the resistance, most versatile

resistance lies between the fulcrum and the force. always a force advantage and is rare in the human body. can be found in the jaw.

force lies between the fulcrum and the resistance and it increase speed and ROM

in activities involving implements the longer the lever (RA) the greater the linear velocity of the ball V= (w)(r)
it requires more muscle force to move the implement

changes the effective direction of the applied force, no change to the force effect. finger tendons work because they are held by ligaments which act as pulleys

not in the human body. changes direction of the applied force and increase the effect of the force.

point of a body where all body weight seems concentrated. balance point and axis of rotation.

depends on position of the body segments, arrangement of the body segments at any given time. in anatomical position it is located where the sagital, frontal and horizonal places intersect.. roughly around the pelvis

area defined by straight lines connecting the most peripheral points of the body parts contacting the supporting surface

static activities remain balanced if the line of action of weight force from the center of mass passes through some part of the base support.

the center of mass falls outside the base of suppose at some point during motion = dynamic stability. this creates torque and can assist move. rising from a chair, running.

a bodies resistance to losing its static or dynamic equilibrium or its resistance to state of motion. two types linear and rotary

resistance to being moved in a straight line. usually where the body is being slid accross some surface either horizonal/vertical or at an incline. the greater the linear force required to upset the linear equilibrium of a body, the more linearly stable the body. objects with more mass(greater inertia)= more stable

resistance to being tipped over. the more rotary stable a body, the greater the angular force necessary to upset the rotary equilibrium

-increasing the size of the base of support to the direction of the applied force. the line of gravity has further to travel before it moves outside the BOS
- decreasing the height of the center of mass
-change the postition of the line of gravity inside the BOS

it is a tool used to draw what we know in relation to the kinetics of the system

when an object remains at rest or in uniform motion, this is linear force = o and so does angular torque

mechanical work done on a body by a force is equal to the product of the forces magnitude and displacement of the body in the direction of the force that occurs while the forces is being applied to it
W=Fd W is mechanical work done by the force, F is the magnitude of the force, and d is the displacement in the direction of the force.

if the forces acts in the same direction as the body moves it is positive work. zero work is done when the object does not move. if force acts in the opposite direction as the body moves it is negative work.

amount of mechanical work done in a particular time period. power is important when a slow application of force will not do the job.

the product of force and the linear velocity of the muscle shortening P=FV

the rate of torque production at a joint, the product of net torque and the angular velocity at a joint. P=Tw

capacity to do work and is a scalar quantity.
nrg can be transformed from one type to another

is a body having energy because of its motion, position relative to early state of development. two forms kinetic(translational and rotational) and potential (gravitational and strain)

the capacity of a body or object to do work while it reforms after being deformed (stretching or compressed).

the increase in length(extension) of a spring is proportional to the applied force
F=-k(spring constant)x(length after deformation-length before.. aka extension).
applied force does work during the spring extension and this is stored as strain energy

total work under force-displacement graph.
work

energy can be stored but work cannot. work is the process of changing energy from one form to another.

it is equal to the sum of the changes in kinetic and potential energy. positive work implies an increase in energy of that body.negative work implies a decrease in energy