Biomechanics - angular motion

Question 1

What is the definition of angular motion

Answer 1

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

Question 2

eg of angular rotation

Answer 2

a gymnast whole body will rotate will rotate around a bar (axis of rotation)

Question 3

What is an eccentric force

Answer 3

a force applied outside the centre of mass, resulting in angular motion

Question 4

What is torque

Answer 4

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

Question 5

What does angular motion result from

Answer 5

an eccentric force being applied to a body where the force is applied outside the centre of a body’s mass

Question 6

What is the principal axis of rotation

Answer 6

an imaginary line that passes through the centre of mass about which a body rotates: longitudinal, transverse and frontal axis

Question 7

What is the longitudinal axis of rotation

Answer 7

From head to toe through the centre of mass

A body rotating around the longitudinal axis would be performing actions such as a flat spin on the ice or full turn in trampolining

Question 8

What is the transverse axis of rotation

Answer 8

left to right through centre of mass

a body rotating around the transverse axis would be performing actions such as sommersults

Question 9

What is the frontal axis of rotation

Answer 9

front to back through the centre of mass

a body rotating around the frontal axis be performing actions such as cartwheels

Question 10

3 key descriptors important for angular motion

Answer 10

1- angular velocity
2- movement of inertia
3-angular momentum

Question 11

What is angular motion measured in

Answer 11

radians

Question 12

What is a radian

Answer 12

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

Question 13

Calculation of angular velocity

Answer 13

angular displacement
/
time taken

Question 14

What is angular velocity

Answer 14

the rate of change in angular displacement measured in radians per second (rate of spin)

Question 15

How is angular velocity measured

Answer 15

in radians per second (rad/s)

Question 16

What is moment of inertia

Answer 16

the resistance of a body to change its state of angular motion or ration

A resting body will not want to start rotating around an axis and

a rotating body will not want to change its angular motion or movement

it will resist increasing or decreasing the rate of spin

Question 17

How can moment of inertia be calculated

Answer 17

sum of (mass x distributution of the mass from the axis of rotation)

Question 18

How is moment of inertia measured

Answer 18

kgm2

Question 19

Two factors that affect moment of inertia

Answer 19

mass- greater mass= greater moment of inertia

and
distribution of mass from axis of rotation- further mass moves from axis of rotation = greater movement of inertia

Question 20

If moment of inertia is high - what is the resistance to rotation and angular velocity and rate of spin

Answer 20

resistance to rotation- high
angular velocity is low
rate of spin - slow

Question 21

If moment of inertia is low - what is the resistance to rotation and angular velocity and rate of spin

Answer 21

resistance to rotation- low
angular velocity- high
rate of spin- fast

Question 22

How would an ice skater manipulate their body to reduce moment of inertia

Answer 22

bringing arms and legs closer to midline ot body) = rotate quicker

Question 23

How would an ice skater manipulate their body to increase moment of inertia

Answer 23

moving limbs away from midline of the body

reduces angular velocity and decreases rate of spin

Question 24

What is angular momentum

Answer 24

the quantity of angular motion possessed by a body

Question 25

equation for angular momentum

Answer 25

moment of inertia
x
angular velocity

Question 26

What is angular momentum measured

Answer 26

kgm2rad/s

Question 27

To start rotating around an axis what must be generated in the preparation/ take off phase of rotational movement?

and what must be applied

Answer 27

momentum

eccentric force or torque must be applied

Question 28

How does a high-board diver create rotation

Answer 28

jump away from the board

they lean away from board at take off so the reaction force generated from the diving board passes outside their centre of mass

(they lean back to create a spinning effect)

this creates an eccentric force applied to the body, the greater the quantity of angular momentum generated for the movement

Question 29

Extend your knowledge-
Newtons laws of motion have angular ‘versions’ known as…….

Answer 29

analougues

Question 30

What is the analogue of newtons second law of motion

Answer 30

‘the rate of change in angular momentum of a body is directly proportional to the size of the eccentric force (torque) applied

and takes place in the same direction as the eccentric force is applied

Question 31

Extend your knowledge
Linking to a diver- what will a greater eccentric force applied to the diver at take off from the board lead to

Answer 31

the greater the rate of change in angular momentum generated

Question 32

What is conservation of angular momentum

Answer 32

angular momentum is a conserved quantity which remains constant unless an external eccentric force or torque is applied

Question 33

What is angular analogue of newtons first law of motion

Answer 33

the angular equivalent of newtons first law of motion
- which states a rotating body will continue to turn about its axis of rotation with constant angular momentum
unless acted upon by an eccentric force or external torque

Question 34

A moment of inertia increases, angular velocity …………..

Answer 34

decreases

Question 35

Once angular momentum is generated does it change throughout movement

Answer 35

no it remains constant

known as a conserved quantity

means performer can continue rotating for a long period of time

Question 36

Key descriptors of angular motion

Answer 36

movement of inertia, angular velocity and angular momentum.