Angular motion

Question 1

angular motion

Answer 1

• when a body/part of a body moves in a circular path
• about an axis of rotation

Question 2

gymnast giants on bars -

Answer 2

• whole body rotation
• 360 degrees
• axis of rotation = bars

Question 3

running

Answer 3

• part body rotation
• hip joint = axis of rotation in flexion & extension
• leg moving around hip joint

Question 4

trampoline somersault

Answer 4

• CoM = axis of rotation
• whole body rotation
• 360 degrees

Question 5

creation of angular motion

Answer 5

• forces line of application passes outside the centre of mass of a body’s mass
• termed eccentric force or a torque

Question 6

eccentric force / torque

Answer 6

turning or rotational force

Question 7

example - how angular motion is created through tennis ball

Answer 7

• eccentric force applied outside CoM of tennis ball
• causing resultant motion of angular motion/spin
• also termed a torque = a turning rotational force

Question 8

compare angular motion and linear motion - A01

Answer 8

• linear motion is when body/part of body moves in a straight/curved line
• in a constant distance, displacement, time velocity
• angular motion is when body/part of a body moves in a circular path about an axis of rotation

Question 9

compare angular motion & linear motion

Answer 9

• linear motion created when a direct force passes through bodies centre of mass
• angular motion is created when forces line of application passes outside the centre of a bodies mass - via an eccentric force

Question 10

compare angular motion & linear motion - A02

Answer 10

• linear motion = toboggan/ski jumper after take off/bike frame
• angular motion = gymnastics somersault/running at hip joint/ all moving joiunts

Question 11

what will an eccentric force cause angular rotation around

Answer 11

• 3 principal axis of rotation
• through CoM of a body

Question 12

3 axis of rotation

Answer 12

• longitudinal
• transverse
• frontal

Question 13

longitudinal axis

Answer 13

• runs vertically through CoM of a body
• from top to bottom

Question 14

example of longitudinal axis

Answer 14

• ice skater spinning on ice
• dancer performing pirouette

Question 15

transverse axis

Answer 15

• runs horizontally through CoM of a body
• from side to side

Question 16

example of transverse axis

Answer 16

• gymnastics somersault

Question 17

frontal axis

Answer 17

• runs horizontally through the CoM of a body
• from front to back

Question 18

example of frontal axis

Answer 18

sideways cartwheel

Question 19

planes and axis -

Answer 19

• a body will perform movement through a plane
• and around an axis

Question 20

axis

Answer 20

• an imaginary line passing through the CoM
• about which the body or limb rotates

Question 21

pair up the planes and axis

Answer 21

• sagittal plane = transverse axis
• frontal plane = frontal axis
• transverse plane = longitudinal axis

Question 22

movements at sagittal plane

Answer 22

• flexion and extension

Question 23

movements at frontal plane

Answer 23

abduction & adduction

Question 24

movements at transverse plane

Answer 24

rotation

Question 25

angular motion quantities

Answer 25

- angular velocity - moment of inertia - angular momentum

Question 26

angular velocity

Answer 26

- rate of change in angular displacement/rotation

Question 27

angular velocity calculation

Answer 27

angular displacement / time

Question 28

angular velocity units of measure

Answer 28

rad/s - radians per second

Question 29

moment of inertia

Answer 29

- resistance of a rotating body - to change its state of angular motion

Question 30

moment of inertia calculation

Answer 30

- sum of: mass x distribution of mass from axis of rotation

Question 31

angular momentum

Answer 31

- quantity of angular motion possessed by a moving body

Question 32

angular momentum calculation

Answer 32

moment of inertia x angular velocity

Question 33

angular momentum units of measure

Answer 33

kgm squared rads/s

Question 34

compare angular velocity & angular speed

Answer 34

- both measure rate of rotation - but angular velocity indicates direction of spin

Question 35

radian

Answer 35

- measure of the angle through which a body rotates

Question 36

moment of inertia - key concepts

Answer 36

- a static body is reluctant to start rotating around an axis of rotation - a rotating body is reluctant to stop rotating around an axis of rotation

Question 37

moment of inertia - units of measurment

Answer 37

- kgm squared - kilogram metres squared

Question 38

2 factors that affect moment of inertia

Answer 38

- mass of the body - distribution of mass from axis of rotation

Question 39

how does mass of a body affect moment of inertia

Answer 39

- greater the mass of a body - greater moment of inertia - sport requiring higher levels of rotation often have a lower mass - to help lower moment of inertia and increases angular rotation - e.g gymnasts (simone biles) - this cannot change during performance

Question 40

how does distribution of mass from axis of rotation affect moment of inertia

Answer 40

- the further away the mass from axis of rotation - greater the moment of inertia & vice versa - can change during performance & so more significant

Question 41

how do we manipulate body position to increase or decrease moment of inertia

Answer 41

- by making body mass closer/further from axis of rotation - therefore increasing or decreasing angular velocity

Question 42

rank straight back, pike back, tuck back from highest to lowest moment of inertia

Answer 42

- 1. straight = mass is distributed further from CoM/axis of rotation = increased moment of inertia & decreased angular velocity - 2. pike = in the middle - 3. tuck = mass is distributed closest from CoM/axis of rotation decreasing moment of inertia & increasing angular velocity

Question 43

explain how an ice skater manipulates their mass when spinning about the longitudinal axis

Answer 43

- bring their arms & leg close to their CoM - so mass is distributed closer to axis of rotation - decreasing moment of inertia - increasing angular velocity - so they rotate

Question 44

how can an ice skate stop and come out of a spin

Answer 44

- bring their arms & leg outward - to their mass is distributed further from CoM - increasing moment of inertia - decreasing angular velocity - so they stop

Question 45

explain importance of high elbow during front crawl recovery swimming stroke

Answer 45

- swimmer brings arm & elbow closer to axis of rotation - which decreases moment of inertia - increases angular velocity - to alter speed of recovery in the stroke

Question 46

why is the drive leg moving slower than recovery leg in a running stride

Answer 46

- drive leg = - mass of runners leg is distributed further from hip joint (axis of rotation) - increasing moment of inertia & angular velocity - recovery leg = - runner brings leg closer to the axis of rotation (hip joint) - decreasing moment of inertia & increasing angular velocity for recovery

Question 47

what drills do sprinters do to keep their mass closer to axis of rotation (their hip)

Answer 47

- heel flicks - high knees - to keep recovery leg closer to hip