Biomechanics 2

Question 1

Definition of angular motion

Answer 1

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

Question 2

Definition of eccentric force

Answer 2

force applied outside centre of mass resulting in angular motion

Question 3

Definition of torque

Answer 3

measure of turning force applied to body

Question 4

What is linear motion created by

Answer 4

• direct force

- external force passes through the centre of mass

Question 5

Name a sporting example in linear motion

Answer 5

skeleton bob at top speed

Question 6

What is angular motion created by

Answer 6

• eccentric force

- external force passes outside the centre of mass

Question 7

Name a sporting example in angular motion

Answer 7

• gymnastics somersault
• drive and recovery leg rotating about the hip joint of a runner
• arm rotating about the shoulder joint of a tennis player serving

Question 8

What is principal axis of rotation

Answer 8

imaginary line that passes through centre of mass about which a body rotates:

longitudinal, transverse and frontal axis

Question 9

Name the 3 axis’ of rotation

Answer 9

• longitudinal
• transverse
• frontal

Question 10

What is the longitudinal axis

Answer 10

-runs from head to toe through the centre of mass

Question 11

What is the transverse axis

Answer 11

from left to right through the centre of mass

Question 12

What is the frontal axis

Answer 12

runs from back to front through center of mass (cartwheel)

Question 13

Name the 3 descriptors important to angular motion

Answer 13

• angular velocity
• moment of inertia
• angular momentum

Question 14

What is angular velocity

Answer 14

rate of velocity at which an object is rotating around a center or a specific point

Question 15

Give the equation for angular velocity

Answer 15

angular displacement / time taken

Question 16

What is angular velocity measured in

Answer 16

rad/s

Question 17

What is moment of inertia

Answer 17

resistance of body to change its state of angular motion/ rotation.

Question 18

Give the equation for moment of inertia

Answer 18

sum of (mass x distribution of mass from axis of rotation)

Question 19

What is moment of inertia measured in

Answer 19

kgm2

Question 20

Name 2 factors that effect moment of inertia

Answer 20

• mass

- distribution of mass from the axis of rotation

Question 21

Why are complex twists typically performed by athletes with a low mass

Answer 21

• low mass decreases moment of inertia & resistance to change state of rotation
• so athletes can start rotation, change rate of rotation and stop rotation with ease

Question 22

How does mass affect moment of inertia

Answer 22

• greater the mass the greater moment of inertia

- lower the mass the lower the moment of inertia

Question 23

How does distribution of mass from the axis of rotation affect moment of inertia

Answer 23

• further the mass moves from the axis of rotation, greater the moment of inertia
• closer the mass moves from the axis of rotation, lower the moment of inertia

Question 24

How does close ‘tucked’ mass distribution affect moment of inertia

Answer 24

decreases moment of inertia and the resistance to change state of rotation

Question 25

When running what is the recovery leg’s moment of inertia and why

Answer 25

recovery legs mass is distributed close to axis of rotation at hip so moment of inertia is low

-resistance to rotation is low and leg moves back to ground quickly

Question 26

When running what is the drive leg’s moment of inertia and why

Answer 26

drive legs mass is distributed far from axis of rotation at hip so moment of inertia is high

-resistance to rotation is high and leg moves slowly

Question 27

How does moment of inertia effect angular velocity

-when moment of inertia is high

Answer 27

• when moment of inertia is high- resistance to rotation is also high
• so angular velocity is low and so rate of spin is slow

Question 28

How does moment of inertia effect angular velocity

-when moment of inertia is low

Answer 28

• when moment of inertia is low- resistance to rotation is also low
• so angular velocity is high and so rate of spin is fast

Question 29

What is angular momentum

Answer 29

quantity of angular motion possessed by a body

Question 30

Give the formula for angular momentum

Answer 30

moment of inertia x angular velocity

Question 31

What is angular momentum measured in

Answer 31

Kgm2rad/s

Question 32

What is the conservation of angular momentum

Answer 32

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

Question 33

How do you rotate around an axis

Answer 33

• angular momentum must be generated

- preparation phase: eccentric force or torque must be applied

Question 34

What is linear motion

Answer 34

movement of body in straught or curved line where all parts move same distance, in same direction over same time

Question 35

What is direct force

Answer 35

force applied through centre of mass resulting in linear motion

Question 36

What is distance and what is it measured in

Answer 36

total length covered from start to finish

-measured in metres (m)

Question 37

What is displacement and what is it measured in

Answer 37

shortest straight line rout from start to finish

-measured in metres (m)

Question 38

What is speed, what is it measured in, formula

Answer 38

rate of change in distance

-measured : (m/s) (s) (m)

speed = distance / time taken

Question 39

What is velocity, what is it measured in, formula

Answer 39

rate of change in displacement

-measured: (m/s) (s) (m)

velocity = displacement / time taken

Question 40

What is acceleration, what is it measured in, formula

Answer 40

rate of change in velocity

-measured: (m/s/s) (m/s) (s)

acceleration = (final velcocity - initial velocity) / time taken