Angular Motion Flashcards
Definition of angular motion
When a body/part of a body moves in a circular path about an axis of rotation
What is the axis of rotation called in a joint?
Fulcrum
What are the 3 things you can say to describe angular motion?
Whether it’s whole/part of a body
Whether it’s a whole circle/part of a circle
The axis of rotation (normally a joint)
How is angular motion created?
When a forces line of application passes outside the centre of mass of a body’s mass. This is termed an eccentric force/torque
What is the definition of torque?
A turning or rotational force
What is the resultant motion made from an eccentric force?
Angular motion/spin
Definition of longitudinal axis of rotation?
Runs vertically through the centre of mass of a body from the top to bottom (head to toes)
Definition of transverse axis of rotation?
Runs horizontally through the centre of mass of a body from side to side (left to right)`
Definition of frontal axis of rotation?
Runs horizontally through the centre of mass of a body from front to back (through belly button)
Example of longitudinal axis of rotation?
Dancer performing a pirouette
Example of transverse axis of rotation?
Gymnast performing a front/back somersault
Example of frontal axis of rotation?
Gymnast performing a cartwheel
Definition of an axis of rotation?
An imaginary line that passes through the centre of mass about which the body/limb rotates
What plane/axis of rotation does flexion/extension occur in?
Plane - sagittal
Axis of rotation - Transverse
What plane/axis of rotation does abduction/adduction occur in?
Plane - Frontal
Axis of rotation - Frontal
What plane/axis of rotation does rotation occur in?
Plane - Transverse
Axis of rotation - Longitudinal
Definition of angular velocity?
Rate of change in angular displacement/rotation
Calculation for angular velocity?
Angular displacement / Time
Units of measurement for angular velocity?
Rad / s
Definition for moment of inertia?
Resistance of a rotating body to change its state of angular motion
Calculation for moment of inertia
MI = Sum of mass X r squared
r squared = distribution of mass from the axis of rotation squared
Units of measurement for moment of inertia
kgm squared
Definition of angular momentum
The quantity/amount of angular motion possessed by a rotating body
Calculation for angular momentum
Moment of inertia X Angular velocity
Units of measurement for angular momentum
kgm squared rad/s
Definition of radian
A measure of the angle through which a body rotates
Degrees/180 X pi
What are the 2 factors that affect the moment of inertia?
Mass of the body
Weight in relation to your axis of rotation
How does a mass of a body affect the moment of inertia?
The larger the mass of a body the greater the MI (can’t change during performance)
Why do athletes doing sports requiring high levels of rotation normally have a lower mass?
Decreases moment of inertia (the resistance of a body to start rotating) so increases angular rotation
How does the weight in relation to your axis of rotation affect the moment of inertia?
The further away the mass from the axis of rotation, the greater the moment of inertia so lower angular velocity.
Can be changed during performance and therefore, more significant during performance.
What is the parabolic curve for a diver?
Flight path of the centre of mass (can’t be changed during flight)
When is angular motion generated?
When the centre of mass passes outside the base of support. A force is applied outside the centre of mass, termed an eccentric force creates angular momentum.
What is the analogue that goes with angular momentum relating it to N1?
A rotating body will continue to rotate around it’s axis of rotation with constant angular momentum unless acted upon by an eccentric force.
What is the analogue that goes with angular momentum relating it to N2?
The rate of change in angular momentum of a body is directly proportional to the size of the eccentric force and occurs in the same direction as the eccentric force is applied
What is always constant angular velocity, moment of inertia or angular momentum?
Angular momentum
