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Sport - Biomechanics > Angular Motion > Flashcards

Angular Motion Flashcards

1
Q

Definition of angular motion

A

Movement of a body or part of a body in a circular path about an axis of rotation

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2
Q

Definition of eccentric force

A

A force applied outside the centre of mass resulting in angular motion

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3
Q

Definition of torque

A

A measure of the turning (rotation or eccentric) force applied to a body

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4
Q

Definition of principal axis of rotation

A

An imaginary line that passes through the CoM about which a body rotates

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5
Q

What are the 3 axis of rotation?

A

Longitudinal, transverse, frontal

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6
Q

What is a sporting example of angular motion?

A

A gymnast rotating around the bar, an athletes leg rotating at the hip, a divers body rotating around their CoM, a ball rotating in the air, trampolinsit body rotates around CoM during a somersault

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7
Q

What are the three planes?

A

Sagittal, Frontal, Transverse

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8
Q

What does angular motion result from?

A

An eccentric force being applied to a body, where the force is applied outside the centre of mass

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9
Q

How is eccentric force measured?

A

As torque

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10
Q

What is the acronym to remember the planes and axis?

A

Twists Test Laziness
Cartwheel Feel Funny
Somersaults Sometimes Tumble

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11
Q

What is the comparison of linear motion and angular motion?

A

-Linear motion is movement of a body in a straight or curved line where all parts move the same distance, in the same direction over the same time BUT angular motion is the movement of a body in a circular path about an axis of rotation
-Linear motion is created by an external force passing through the CoM BUT angular motion is created by an eccentric force, an external force passes outside the centre of mass
-An example of linear motion is skeleton BUT an example of angular motion is a somersault in gymnastics or arm rotating about the shoulder joint of a tennis player serving

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12
Q

What movements occur at the sagittal plane?

A

Flexion and extension

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13
Q

What movements occur at the transverse plane?

A

Rotation, (and supination, pronation)

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14
Q

What movements occur at the frontal plane?

A

Abduction, adduction

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15
Q

What is the longitudinal axis?

A

Runs from the head to toe through the centre of mass

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16
Q

Give a sporting example of a movement on the longitudinal axis

A

Flat spin on ice, full turn in trampolining, slalom skiing, change of direction in tennis

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17
Q

What is the transverse axis?

A

Runs from left to right at the hips through the centre of mass

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18
Q

What is a sporting example of a motion through the transverse axis?

A

Somersault, running

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19
Q

What is the frontal axis?

A

Runs from front to back through the centre of mass

20
Q

What is a sporting example of a motion through the frontal axis?

A

Star jump, cartwheel in gymnastics

21
Q

Defintion of radian (rad)

A

A unit of measurement of the angle through which a body rotates

22
Q

What is 1 radian equal to?

A

57.3 degrees

23
Q

Definition of angular velocity

A

The rate of change in angular displacemen

24
Q

What is angular velocity measured in?

A

radians per second (rad/s)

25
What is the equation to calculate angular velocity?
Angular velocity = angular displacement / time
26
What is angular velocity measured in?
Radians per second (rad/s)
27
Definition of moment of inertia
the resistance of a body to change its state of angular motion or rotation
28
How do you calculate moment of inertia?
moment of inertia = sum off (mass x distribution of mass from the axis of rotation squared) MI = ∑m x r^2
29
What is moment of inertia measured in?
Kgm2
30
What are the two factors affecting moment of inertia?
Mass and distribution of mass
31
How does mass affect the moment of inertia?
The greater the mass of a body the greater the moment of inertia. Low mass decreases moment of inertia and resistance to change state of motion, so athletes can state, stop and change rotation easier
32
Explain why certain sports people like divers and gymnasts typically have a lower mass?
They will have a lower mass, to help decrease their moment of inertia and their resistance to change state of rotation
33
Explain distribution of mass as a factor affecting inertia
The further the mass is from the axis the greater the moment of inertia. If the mass is closer to the axis the moment of inertia is lower
34
Explain how a gymnast showcasing a tight tuck front somersault affects her movement of inertia?
A gymnast performing a tucked somersault, will have a tight tuck, the mass will be closer to the axis of rotation so moment of inertia and resistance to change state of motion will be lower. She will face less resistance to rotation and rotate quicker than if she was doing a straight front somersault
35
Explain the effect of moment of inertia on angular velocity
If the moment of inertia is high, resistance to rotation is also high, therefore angular velocity is low, the rate of spin is slower If the moment of inertia is low, resistance to rotation is also low, therefore angular velocity is high, the rate of spin is fast
36
Definition of angular momentum
The quantity of angular motion possessed on a body
37
How do you calculate angular momentum?
angular momentum = moment of inertia (kgm2) x angular velocity (rad/s)
38
What are the units of angular momentum?
kgm2rad/s
39
Definition of conservation of angular momentum
Angular momentum is a conserved quantity which remains constant unless an external force or torque is applied
40
Definition of angular analogue of Newtons 1st law
A rotating body will continue to turn about its axis with constant angular momentum unless acted on by an eccentric force or external torque
41
Explain the conservation of angular momentum?
Once generated angular momentum does not change throughout the movement, if momentum of inertia increases then angular velocity decreases and vise versa. It remains constant so is termed ‘conserved’. One in flight, angular momentum cannot be changed but performer can manipulate moment of inertia and therefore angular velocity to maximise their performance by including complex twists and spins
42
Explain how this ice skater performs her axel jump in terms of angular motion
-Generates angular momentum by applying an eccentric force from the ice to their body -Skater starts to rotate about the longitudinal axis -Their distribution of mass is away from the longitudinal axis as their arms and one leg are held away from the midline. The moment of inertia is high and therefore angular velocity is low. As the go into the jump they wil rotate slowly and with control -Picture B shows that during the flight the ice skater distributes their mass close to the longitudinal axis as they tuck in their arms and legs. The moment of inertia is decreased, ands angular velocity is increased so they spin quickly -Picture C shows how in preparation to land the ice skater distributes their mass away from the longitudinal axis, opening out their arms and one leg. The moment of inertia is raised and angular velocity is reduced, they decrease their rate of spin, increasing control of landing, preventing over rotation -As they land, the ice applies an external torque to remove the conserved quantity of angular momentum maintained throughout the jump to move away slowly
43
Plot a graph for the relationship between moment of inertia, angular velocity and angular momentum
44
Explain this graph for a diver performing a one and a half somersault to the water
-At take off the diver generates angular momentum by an eccentric force from the springboard acting on the body and starts the rotation about the transverse axis -Their distribution straight body position distributes mass away from the transverse axis, the moment of inertia is high, angular velocity is low, the diver will rotate slowly and complete the dive with control -During flight the divers tucked position distributes mass away close to the transverse axis. Moment if inertia is decreased, angular velocity is increased, the diver will rotate quickly -Preparing to land the divers straightened body position distributes mass away from transverse axis, movement of inertia is increased and angular velocity is decreased, the rate of spin decreases, gaining control for entry into the water -Angular momentum is conserved throughout
45
What is torque measured in?
Newton meters
46

Sport - Biomechanics (11 decks)

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