Biomechanics key terms Flashcards
Angular momentum
the quantity of rotation a body possesses, and is a product of inertia and angular velocity
Moment of inertia
the body’s reluctance to rotate/ alter its rate of rotation
Angular velocity
The rate of rotation of a body around its axes of rotation
Angular acceleration
The rate of change of angular velocity
Angular displacement
the smallest change in angle between starting and finishing point
Principle of conservation
states that angular momentum remains constant, if moment of inertia decreases, angular velocity increases visa versa
Angular momentum equation
angular momentum = moment of inertia x angular velocity
Angular velocity equation
Angular velocity = angular displacement /time taken
Angular acceleration equation
angular acceleration = change in angular velocity / time taken
How do you calculate angular displacement?
1 radian = 57.3 degrees
Fluid mechanics
Study of an object as it moves through liquid/gas
Surface drag
friction between the surface of an object and the environment (e.g shaving legs)
Form drag
impact of the fluid environment on the object (e.g streamline)
Projectile motion
refers to the movement of either an object or human body through air
Parabola
uniform curve that is symmetrical at its highest point
Impulse
change in momentum of object when the object is acted upon by a force for a period of time
Impulse equation
impulse = force x time
What is the Bernoulli principle?
covers lift force and downward force
Law of Inertia (1)
the resistance an object has to change in its state of motion
- object will remain stationary until force is applied to it
Law of acceleration (2)
size and direction of the force applied is directly proportional to the force causing change
force = mass x acceleration
Law of action/ reaction (3)
to every action there is an opposite and equal force
e.g ground reaction force
Speed
rate of change of position
Distance
length of path a body follows when moving from 1 position to another
distance = speed x time
Centre of mass
point of concentration of the mass/ point of balance of the body
External forces
forces from outside the body
Internal forces
Forces from within the body
(e.g muscle contractions)
Static friction
force exerted on 1 surface by another when there is no motion between the two surfaces
Sliding friction
occurs when dry friction acts between 2 surfaces that are moving relative to each other
Angular motion
occurs as a result of torque.
Torque
rotational consequence as a result of force
torque (Nm) = size of force x moment arm
Moment arm
perpendicular distance from fulcrum to where force is applied
(larger the distance the larger the torque)
Linear motion
motion in a straight line or curved line, with all body parts moving in the same direction at the same speed and same distance
First class lever
Fulcrum is positioned between the effort and resistance (load)
Second class lever
Load between fulcrum and effort
Third class lever
Effort between fulcrum and load
First class lever example
Extension at elbow
Second class lever example
Plantar flexion
Third class lever example
Flexion at elbow
Mass
quantity of matter in the body (kg)
Weight
the gravitational force exerted on an object (N)
Velocity
rate of change of displacement (m/s)
Acceleration
the rate of change of velocity (m/s squared)
Momentum
the product of the mass and velocity of an object (Kgm/s)
Friction can be affected by:
surface characteristics
temperature of surfaces
mass of objects that are sliding
Air resistance
opposes the motion of an objects that move through air
Air resistance is affected by
velocity
shape and characteristics of moving body
cross-sectional area of the moving body
Impulses can be increased by:
less time, more force
An increase in impulse will result in an increase in the rate of momentum, causing changes to velocity. Therefore impulse is equivalent to a change in momentum of a body as a result of a force acting upon it
Horizontal displacement
the shortest distance from starting point to the finishing point in a line parallel to the ground
If landing height is higher than release height what is the optimum release point?
optimum release point is above 45 degree
If release height and landing height are the same what is optimum release point?
optimum release point is equal to 45 degrees
if release height is higher than landing height what is optimum release point?
optimum release point is below 45 degrees
Factors affecting horizontal displacement:
angle of release
speed of release (greater the release velocity - greater the horizontal displacement)
height of release (greater the release height = increase in horizontal displacement)
Factors reducing drag:
- Velocity of moving body
- Cross-sectional area of moving body
- Shape and surface
- Characteristics of the moving body
Factors affecting stability:
Height of centre of mass
Area of base of support
Position of line of gravity
Body mass
