Angular and Linear Motion Flashcards
Define linear motion?
Movement of a body in a straight or curved line where all parts move the same distance in the same direction at the same time.
DDT- distance , direction , time
Direct force is applied directly through COM
What does a scalar measurement refer to?
A size/ quantity of motion, but no direction specified
S= Simple
eg: distance, speed, mass, inertia
What does a vector measurement refer to?
A size/ quantity of motion with a specified DIRECTION OF MOVEMENT
eg: acceleration, deceleration, velocity , weight, momentum, displacement
Define distance and how to calculate?
Total length covered from start to finish (m)
SCALAR
eg: swimming 4 lengths of a 50m pool= a distance of 200m
Define displacement and how to calculate?
The shortest straight line from start to finish (m)
VECTOR
eg: swimming 4 lengths of a 50m pool= a displacement of 0m.
Define speed and how to calculate?
The rate of change of position/distance (m/s)
SCALAR- doesn’t consider direction
speed= distance/ time= (m/s)
Define velocity and how to calculate?
The rate of change of displacement (m/s)
VECTOR
velocity= displacement/ time taken (m/s)
Define acceleration and how to calculate it?
Acceleration is the rate of change in velocity
VECTOR
Acceleration= final velocity- initial velocity/ time taken
(m/s/s)
(large m/s- small m/s times by largest time) (m/s/s)
Will always be a POSITITVE VALUE
Define deceleration and how to calculate it?
The rate of change in velocity is negative and there’s a decrease in velocity.
VECTOR
Same equation as acceleration
Draw a DISTANCE TIME graph?
What does the graph show?
Always plot TIME on the HORIZONTAL AXIS
The relationship represents the increase in distance per unit of time.
What does a straight line mean on a DISTANCE TIME graph?
Rest or Stationary
What does a horizontal line show on a DISTANCE TIME graph?
Constant velocity
=balanced forces
What does a curve upwards show on a DISTANCE TIME graph?
Acceleration
=unbalanced forces
=increase in distance per unit of time
What does a curve downwards show on a DISTANCE TIME graph?
Decelerating
=unbalanced forces
=decrease in distance per unit of time
What does a horizontal line mean on a SPEED TIME graph?
Acceleration
What does a SPEED TIME graph show?
The increase of speed over an amount of time.
What does a downwards horizontal line mean on a SPEED VELOCITY graph?
Decelerating
rest or stationary= line at 0 on speed
What does a VELOCITY TIME graph show?
The increase in velocity/ decrease in velocity over an amount of time
(has a DISTANCE)
What does it mean if there’s a negative line below the horizontal time line on a VELOCITY TIME graph?
A change in a bodies motion
Leads to an increase in velocity per unit of time in the OPPOSITE DIRECTON
Calculate the acceleration of a performer travelling from 2 m/s to 7 m/s over 1 to 3 seconds?
Final velocity= 7
Initial velocity= 2
(3-1= TIME TAKEN= 2 seconds)
=7/2= 2.5 m/s/s
A swimmer completes three lengths of a 50m pool, define distance and displacement and calculate each?
Distance= the total length covered by a body from one position to another
=150m
Displacement= the shortest STRAIGHT LINE route between two points
=50 m
Define angular motion?
Motion in a circular path about a fixed axis of rotation
Measured in radians
How common is Angular Motion?
More common than linear motion due to dynamic nature of most activities
Objects tend to rotate as they pass over a surface eg: F1 car, bike
Projectiles (a body propelled by the exertion of eccentric force) tend to rotate in flight path eg: tennis ball
What causes angular motion?
Results in an ECCENTRIC force ( a force applied outside the COM)
Also known as torque (a turning or rotating force)
Compare linear and angular motion?
Linear motion is movement of a body in a straight line at the same time, in the same distance, in the same direction
Angular motion is the movement of a body in a circular path AROUND AN AXIS OF ROTATION
A DIRECT FORCE- an external force that passes through the COM
A ECCENTRIC FORCE- an external force (or torque) that moves outside the COM
eg: bob skeleton at top speed
eg: the arm rotating around the ball and socket joint of the solder when a tennis player hits the ball
Where does the Longitudinal Axis divide the body?
A vertical division that runs from head to toe (top to bottom )
Rotation, Supination, Pronation
eg: flat spin in ice skating
Where does the Frontal Axis divide the body?
Runs from front to back from the COM
Adduction and Abduction
eg: cartwheel
Where does the transverse axis divide the body?
T= TABLE football player
Runs from left and right through the COM (side to side)
Flexion and Extension
Axis and Plane pairs?
Fit People Sweat A lot
Frontal Axis and Sagittal Plane
eg: Sagittal plane- flexion and extension- about the frontal axis of rotation
Axis and Plane pairs?
Tall People Fall A lot
Transverse Axis and Frontal Plane
Transverse- runs from left to right through COM
Frontal- lies vertical- front and back
Axis and Plane pairs?
Long people Talk Alot- chatty and lanky Caitlin
Longitudinal Axis and Transverse Plane
Longitudinal- head to toe through COM
Transverse- divides the body into Top and bottom
There are a number of descriptors specific to angular motion:
Angular Momentum- the amount of motion a body has during ROTATION
Angular Velocity- rate of movement in ROTATION
Angular Acceleration- rate of change in velocity in ROTATION
Moment of Inertia- resistance of a body to a change of state when ROTATING
Define angular velocity
How do you calculate angular velocity
The rate of change of angular displacement- the rate/ speed of a spin
= angular displacement (radians)/ time taken (s)
= (rad/s)
= how fast they are spinning
What is important to remember with angular speed and angular velocity?
They are interchangeable- speed doesn’t include a direction whereas velocity includes a direction
Define Moment of Inertia (I)
How do you calculate moment of inertia?
The resistance of a body to change it’s state of angular motion/ rotation
Moment of Inertia= mass (kg) x distribution of mass from axis (m2)
=(kg/m2)
What two factors affect MI and are used to calculate (I) ?
The MASS of a body: The greater the mass, the greater the moment of inertia
The lower the mass, the easier it is to change the rate of rotation
Sports with a high degree of rotation are typically performed by those with a low mass eg: figure skater
Low mass= low MI= easier to control spin
The DISTRIUTION of MASS around the AXIS OF ROTATION: the further the mass is from the axis of rotation, the greater the MI (increased resistance)
Movements where the mass is tucked in= lower MI eg: tucked somersault.
Tucked= low MI= faster rotation
Normal= higher MI= slower rotation
What’s the relationship between MI and AV?
If one is high, the other is low= OPPOSITE
To increased AV, need to decrease MI
To increase MI, need to decrease AV
Describe the stage of a skating spin when the skaters arms are out wide?
When their arms are out their mass is distributed far away from their axis of rotation, therefore
- their MI is high
- their resistance to rotation is high
- this means AV is low
- so the speed of their spin is low
Describe the stage of a skating spin when the skaters arms are tucked in?
When their arms are tucked in their mass is distributed closer to their axis of rotation, this means that:
- their MI is low, meaning their resistance to rotation is low
- this means their AV is high
- therefore they spin faster
Define Angular Momentum
How do you calculate angular momentum?
The quantity of angular motion possessed by a moving body
Angular Momentum= MI (kgm2) x Angular Velocity (rad/s)
=(kgm2/rad/s)
-Once generated in the air it remains CONSTANT- cannot be changed in flight so it’s important to generate max angular momentum prior to flight.
What’s Newton’s 1st Law of Angular Motion?
A rotating body will continue in it’s state of angular motion unless an external force or “torque” is exerted upon it.
For example, an ice skater will continue to spin in the air until landing.
What’s Newton’s 2nd Law of Angular Momentum?
The rate of change in angular momentum is proportional to the force causing it and the change takes place in that direction
eg: leaning forwards on a dive board will create more angular motion than standing straight `
What’s Newtons 3rd Law of Angular Momentum?
When a force is applied from one body to another, the second body will exert an equal and opposite force on the other body
eg: in a dive, changing position from a tight tuck to a lay out position.
What does a straight line mean on a SPEED TIME graph?
constant speed/velocity
