A2: Angular Motion Flashcards
Definition of angular motion:
Movement of a body in a circular path about an xis of rotation
What causes angular motion?
Caused by an eccentric force applied outside the body’s centre of mass
Definition of torque:
A measure of turning force applied to a body
What are the 3 principal axes of rotation?
Longitudinal
Transverse
Frontal
Location of longitudinal axis and sporting example:
Runs from head to toe
E.g. Trampoline performs a full twist turn
Location of transverse axis and sporting example:
Runs from side to side
E.g. A front somersault
Location of frontal axis and sporting example:
Runs from front to back
E.g. A cartwheel
What are the 3 descriptors of angular motion?
Moment of inertia (MI) Angular velocity (AV) Angular momentum (AM)
Definition of MI
Resistance of a body to change its state of angular motion or rotation
Calculation and units for MI
Mass x (Distribution of mass from axis of rotation ^2) Measured in kgm^2
Definition of AV
Rate of change of angular displacement or rate of rotation
Calculation and units for AV
Angular displacement / Time taken
Measured in radians/sec
Definition of AM
Quantity of angular motion possessed by a body
Calculation and units for AM
Product of other two descriptors: AV x MI
Measured in kgm^2/s
How does mass affect size of MI of rotating body?
Greater mass = greater MI
Lower mass = easier to change rate of spin
(Diving performed by low mass athletes)
How does distribution of mass from axis of rotation affect MI?
Further from axis of rotation = Greater MI
e.g tucked somersault has low MI, greater rate of spin
How does MI affect AV?
High MI = Low AV
Low MI = High AV
(resistance to rotation means rate of spin is low)
Definition of conservation of angular momentum:
Angular momentum is a conserved quantity so remains constant until an eccentric force or torque is applied
Angular analogue of Newton’s First Law:
A rotating body will continue to rotate about its axis of rotation with constant angular momentum unless acted upon by an eccentric force/torque
Angular analogue of Newton’s Second Law:
A body’s rate of change in angular momentum is proportional to the size of the eccentric force applied, and acts in the same direction
Angular analogue of Newton’s Third Law:
For every force (torque) exerted by a first body on a second body, there will be an equal and opposite force exerted by the second body on the first body
