YR2 LINEAR MOTION & ANGULAR Flashcards
What is linear motion?
The movement of a body in a straight or curved line, where all the parts move the same
distance in the same direction in the same time
What is linear motion caused by?
Linear motion is caused from a direct force applied to the Centre of a body’s mass (the point at which a body is balanced in all directions (weight acts from this
point)
What is distance?
The total length covered from start to distance in positions (m)
What is displacement?
The shortest straight line distance from start to finish
positions (m)
What is speed?
Equation?
The rate of change is distance (m/s)
Speed = Distance ÷ Time taken
What is velocity?
Equation?
The rate of change is displacement (m/s)
Speed = Displacement ÷ Time taken
What is acceleration?
Equation?
The rate of change in velocity (ms-2)
Acceleration = (Final Velocity –Initial Velocity) ÷ Time taken
Positive Value =
Negative value =
Acceleration
Deceleration
Tips for DISTANCE TIME GRAPHS?
Cannot go down (distance cannot decrease)
Gradient is equal to the speed
Tips for VELOCITY TIME GRAPHS?
Curves show acceleration
Can be positive and negative
Tips for SPEED TIME GRAPHS?
Area under is the distance
Positive gradient acceleration negative deceleration
What is Angular motion?
What is it caused by?
Movement of a body or part of a body in a circular path about an axis of rotation
Angular motion is caused from a eccentric force , a force that is applied outside the
center of mass. An eccentric force is also known as torque, a measure of turning
force applied to a body
What is a sporting example of angular motion?
E.g. a trampolinist body will rotate around her center of mass in a somersault
Name 3 axis of rotation?
Longitudinal
Frontal
Transverse
What is Longitudinal axis:?
Example
Running from head to toe through the center of mass.
A performer rotates around this axis in a flat spin on the
ice during ice dance
What is Transverse axis?
Example
Running from left to right through the center of mass.
A performer rotates around this axis in a somersault
in a vault
What is Frontal axis?
Example
Running from back to front through the center of mass.
A performer rotates around this axis in a cartwheel
What are the three Angular motion descriptors?
Angular Velocity
Moment of inertia
Angular Momentum
What is Angular velocity?
Equation?
Measured in?
The rate of rotation-
Angular velocity = angular displacement/time taken
Measured in Radians (rad)
What is moment of inertia?
Equation?
The resistance of a body to change in its state of angular motion or rotation
Moment of inertia = sum of ( mass x distribution of the mass from the axis of rotation squared)
What two factors affect the moment of inertia?
Mass
Distribution of mass
How does mass affect the moment of inertia?
The higher the mass the higher the moment of inertia (why all gymnasts are small)
The lower the mass the lower the moment of inertia (Rugby props are never small)
How does distribution of mass affect moment of inertia?
The higher the distribution of mass the higher the moment of inertia (why pike flips are harder than
somersaults)
The lower the distribution of mass the lower the moment of inertia
When running -
Drive Phase
Recovery Phase
High or low MOI?
Drive phase:
High MI
Large distribution of mass
Recovery Phase:
Low MI
Low distribution of mass
HOW CAN MOMENT OF INERTIA BE
MANIPULATED?
Moment of inertia has a direct impact on velocity:
If there is a high MI then resistance to rotation of high so angular velocity is
slow
If there is a low MI then there is not much resistance to rotation so angular
velocity is high
What is angular momentum?
Equation?
The quantity of angular motion possessed by a
body
Angular momentum (kgm2s-1) = Moment of inertia x angular velocity
What is the CONSERVATION OF ANGULAR
MOMENTUM?
Newton’s Law of inertia: constant velocity until acted upon by an external force
So angular momentum is constant, it cannot be generated during flight but can be
manipulated during flight to allow for velocity changes.
Increase the distribution of mass, you decrease moment of inertia and therefore can decrease velocity to keep angular momentum constant
CONSERVATION OF ANGULAR
MOMENTUM sporting example?
E.G. Tom Daley cannot increase angular momentum mid flight but can increase and decrease velocity due to a manipulation of the equation
Describe the way in which an ice skater
performing a triple axel jump with spin
achieves this using, axis of rotation, angular
velocity and angular momentum?
The Ice skater generates angular motion by applying an eccentric force
The Ice skater starts rotation around the longitudinal axis
The distribution of mass is large so the moment of inertia is increased and angular
velocity it low so they stay in control
The distribution of mass is small so the velocity increases and moment of inertia
decreases (allows for more spins)
The distribution of mass is large so the moment of inertia is increased and angular
velocity lowers, increasing their control for landing
As they land the ice applies external force to remove the angular momentum
