1.3b biomechanics linear motion Flashcards
what is linear motion
movement of a body in a straight or curved line where all parts move the same distance and direction
how is linear motion created
a direct force is applied to a body, where the force is applied directly to/through the com
distance
total length of the path covered from start to finish
distance (m) = speed (m/s) / time (s)
displacement
the shortest straight line route from start to finish
displacement (m) = velocity (m/s) / time (s)
speed
the rate of change in distance
speed (m/s) = distance (m) / time (s)
velocity
the rate of change of displacement
velocity (m/s) = displacement (m) / time taken (s)
acceleration/deceleration
-the rate of change in velocity
acceleration (m/s2) = (final - initial velocity (m/s)) / time taken (s)
acceleration (m/s2) = force (n) / mass (kg)
what is angular motion
movement of a body or part of a body is a circular path about an axis of rotation
how is angular motion applied
from an eccentric force applied to a body and outside of the com
TORQUE - turning or rotational force
how to remember axis of rotation
sam talks for far too long
how does movement at a joint take place
along a plane and about an axis
sam talks - flexion and extension
occurs along the sagittal plane
about the transverse axis
eg somersault
for far - abduction and adduction
occurs along frontal plane
about the frontal axis
eg cartwheel
too long - horizontal flexion and extension
occurs along transverse plane
about longitudinal axis
eg rotating in circle when discuss throwing
how is angular motion measured
radians (rad)
1 rad = 57.3 degrees
what is angular velocity
-the rate of change in angular displacement
-rate of rotation
how do you calculate angular velocity
angular velocity (rad/s) = angular displacement (rad) / time taken (s)
what is moment of inertia
the resistance of a body to change its state of angular motion or rotation
how do you calculate moment of inertia
moment of inertia (kgm2) = sum of (mass (kg) x distribution of mass from axis of rotation2 (m2))
what is angular momentum
the quantity of angular motion possessed by a body
angular momentum calculation
angular momentum (kgm2rad/s) = moment of inertia (kgm2) x angular velocity (rad/s)
what factors affect moment of inertia
mass
distribution of mass
effect of mass on moment of inertia
greater mass = greater MI = slower rate of spin
effect of distribution of mass on moment of inertia
the further the mass moves from the axis of rotation, the greater the moment of inertia
diver move into tucked position to increase angular motion and motion of inertia. stretch out into dive to slow this down
what is the angular analogue of newton’s 1st law of motion
a rotating body will continue to turn about its axis of rotation with constant angular momentum unless acted upon by an eccentric force or external torque
what relationship does moment of inertia and angular velocity have
inverse relationship
one high = other low
what is conservation of angular momentum
a conserved quantity which remains constant unless an external eccentric force or torque is applied
principles of angular momentum
-angular momentum can’t be changed when in flight
-moment of inertia can be manipulated to effect angular velocity
-increase rate of spin or decrease, depending on desired effect
what are fluid mechanics
the study of the forces acting on a body travelling through air (AR) or water (drag)
effect of velocity on fluid mechanics
greater velocity = greater ar/d
effect of mass on fluid mechanics
greater mass = greater ar/d
effect of frontal cross-sectional area on fluid mechanics
greater cross sectional area = greater ar/d
swimmer diving into pool with arms tight to head
effect of streamlining on fluid mechanics
greater streamlining = lower ar/d
sprint cyclist wearing teardrop helmet to make themselves streamlined
effect of surface characteristics on fluid mechanics
smoother the surface characteristics = lower ar/d
sprinter wearing lycra
