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Mr Thomas - PE - Coggle Diagram
Mr Thomas - PE
COM and Stability
CoM - the point at which a body is balanced in all directions; the point from which weight appears to act
Stability - the ability of the body to resit motion and remain at rest, r for a body to withstand a force applied and return it to its original position without damage
Mass of body - greater mass, greater stavility
Height of CoM - lower CoM, greater stability
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Line of gravity - more central LoG, greater stability
Angular motion - the movement of a body part or part of a body in a circular path about an axis of a rotation
Eccentric force - a force applied outside the CoM, resulting in angular motion
Torque - a measure of the turning force applied to the body
Principal axis of rotation - an imaginary line that passes through the CoM about which a body rotates; longitudinal, transverse and frontal axis
Longitudinal - runs from head to toe through the CoM
Transverse - Runs from left to right through the CoM
Frontal - runs from back to from through the CoM
Sporting examples -
Longitudinal - A slalom skier rotating around the pole to change direction. An ice skater perfoming a jump with a spin
Transverse - A gymnast performing a back or front tucked somersault
Frontal - A side somersault on the beam in gymnastics
Angular motion descriptors - Angular velocity - the rate of change in angular displacement or simply rate of rotation
Moment of inertia - the resistance of a body to change its state of angular rotation
Angular momentum - the quantity of angular motion possessed by a body
Moment of inertia - the greater the mass of a body, the greater the moment of inertia. The low mass decreases moment of inertia and the resistance to change the state of of rotation, so athletes can start rotation, change the rate of rotation, and stop rotation with relative ease
If moment of inertia is high, resistance to rotation is also high therefore angular velocity is low: the rate of spin is slow
If moment of inertia is low, resistance to rotation is also low, therefore angular velocity is high: rate of spin is fast
Conservation of angular momentum - Angular momentum is a conserved quantity which remains constant unless an external force or torque is applied
Angular analogue of Newton's first law of motion - The angular equivalent of Newton's first low of motion which states: a rotating body will continue to turn about its axis of rotation with constant angular motion less acted upon by an external force or external torque
Vertical forces
Weight - the gravitational pull that the earth exerts on a body and is measure in newtons
Weight = mass x acceleration
Reaction forces - equal and opposite forces exerted by a body in response to an action force placed upon it and is measure in newtons
Horizontal forces
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Air resistance - the force opposing motion travelling through air. Form of fluid friction. Measured in netwons
Newton's 1st law - That every object will remain at rest or in uniform motion in a straight line unless compelled to change its state by an external force
Newton's 2nd law - A body's rate of change is proportional to the size of the force applied and acts in the same direction as the force applied
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Linear motion - movement of a body in a straight or curved line where all body parts move the same distance, in the same direction overtime
Direct force - a force applied through he CoM resulting in linear motion
Linear motion descriptors -
Distance - total length covered from start to finish positions
Displacement - the shortest straight-line route from start to finish
Speed = distance/time taken
Velocity = displacement/time taken
Acceleration/deceleration = (final velocity - initial velocity)/displacement
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Air resistance and drag key terms -
Velocity - the greater the velocity, the greater the air resistance or drag
Frontal cross-section - the larger the cross-sectional area, the larger the air resistance or drag
Streamlining and shaping - more streamlined/aerodynamic shape of body in motion, the lower the air resistance or drag
Surface characteristics - the smoother the surface, the lower the air resistance or drag