Angular kinetics

Question 1

Definition of kinematics?

Answer 1

The branch of mechanics concerned with the motion of objects without reference to the forces which cause the motion

Question 2

Definition of kinetics?

Answer 2

The branch of mechanics that deals with the actions of forces in producing or changing the motion of masses

Question 3

How to convert radians into degrees?

Answer 3

360 degrees = 2 pi radians

Question 4

Symbol for angular velocity?

Answer 4

Omega - curly w

Question 5

Symbol for angular acceleration?

Answer 5

Alpha

Question 6

How to calculate linear displacement from angular displacement (formula)

Answer 6

theta x radius

where theta = angular displacement measured in radians

Question 7

How is 1 radian defined

Answer 7

The arc with length equal to the radius

Question 8

How to calculate linear speed (tangential velocity) from angular velocity (formula)?

Answer 8

omega x radius

where omega = angular velocity measured in radians

Question 9

What direction does centripetal force act in?

What does centripetal mean?

Answer 9

Inwards along the radius

“Centre seeking”

Question 10

What are the two formulas for calculating centripetal acceleration?

Answer 10

= tangential velocity^2 / radius

= angular velocity^2 x radius

Question 11

Impulse - what is the:

formula?

units?

Answer 11

Force x time

Ns

Question 12

Momentum - what is the:

formula?

units?

Answer 12

Mass x velocity

kg.m.s-1

Question 13

What is another name for torque?

Answer 13

Moment

Question 14

Torque - what is the:

formula?

units?

Answer 14

Force x perpendicular distance to axis of rotation

N.m

Question 15

Torque impulse - what is the:

formula?

units?

Answer 15

Torque x time

N.m.s

Question 16

Angular momentum - what is the:

formula?

units?

Answer 16

Moment of inertia x angular velocity

kg.m2.s-1

Question 17

Moment of inertia - what is the:

formula?

units?

Answer 17

Mass x (radius of rotation)2

kg.m2

Question 18

What is the definition/formula for torque?

Answer 18

Force x the torque/moment arm

“The tendency of a force to cause a rotation about a specific axis”

Not a force but the effect of a force in creating a rotation

Question 19

What is the definition of torque/moment arm?

Answer 19

The shortest distance between the line of action and the centre of rotation

Question 20

What is the definition of moment of inertia?

Answer 20

The resistance of an object to change in angular motion (and is dependent on the axis of rotation)

Question 21

What is an eccentric force?

Answer 21

A force not passing through the centre of mass

Question 22

What is a force couple?

give 2 examples

Answer 22

2 forces of equal magnitude acting on a body at a distance apart from each other

1. gymnast executing a twist about longitudinal axis (applies backwards force with one foot and a forwards force with the) other
2. use of thumb and forefinger to screw open a jar lid

Question 23

What is the formula linking torque to angular acceleration?

Answer 23

Torque = moment of inertia x angular acceleration

Torque = mass x radius [of gyration]2 x mass

Question 24

What is the formula linking the angular acceleration of linked objects to the torque acting on them?

Answer 24

Sum of the torques acting on the linked objects

= angular acceleration x sum of moments of inertia

Question 25

Define the radius of gyration

Answer 25

The distance between the axis of rotation and an imaginary point on the segment where all of its mass would be considered to act if it had the same moment of inertia as the segment

Question 26

Explain (in words) the parallel axis theorem

Answer 26

The moment of inertia around the whole-body centre of mass is equal to the sum of all of the individual segment movements of inertia about their own centre of mass plus their individual masses multiplied by the squared distances between their centres of mass and the whole body centre of mass

Question 27

Explain the parallel access theorem (formula)

Answer 27

Moment of inertia (whole body) = Sum for all segments ( segment moment of inertia + segment mass x distance between segment and whole body centre of mass ^ 2)

Question 28

What is the formula for moment of inertia of a segment about the transverse/ mediolateral axis of the segment?

Answer 28

mass x radius of gyration around transverse/mediolateral axis ^ 2

Question 29

What are two formulae for angular momentum 1 with respect to moment of inertia 1 with respect to radius of gyration

Answer 29

Angular momentum = moment of inertia x angular velocity = mass x radius of gyration^2 x angular velocity

Question 30

What are the units of angular momentum?

Answer 30

kg.m2.s-1 Radians do not appear in this as they are dimensionless

Question 31

What rule denotes the direction of angular momentum?

Answer 31

Right hand rule Perpendicular to plane of motion Anti-clockwise and upwards is usually denoted as positive

Question 32

What is the angular equivalent of Newton's first law of motion?

Answer 32

A body will continue in a state of uniform angular motion unless acted on by an external torque or moment

Question 33

What is the angular equivalent of Newton's second law of motion?

Answer 33

An external torque or moment produces an angular acceleration of a body that is proportional to and in the direction of the torque and inversely proportional to the moment of inertia

Question 34

What is the angular equivalent of Newton's third la of motion?

Answer 34

For every torque or moment exerted by one body on another body there is an equal and opposite torque or moment exerted by the latter body on the former

Question 35

What is the principle of conservation of angular momentum?

Answer 35

If no external torque is applied to a system, angular momentum remains unchanged

Question 36

Explain the principle of moments

Answer 36

For a rigid body in a state of equilibrium the sum of moments about any point must equal zero

Question 37

What is the formula for the angular equivalent of Newton's second law?

Answer 37

Torque = moment of inertia x angular acceleration

Question 38

What is the formula relating torque to angular momentum?

Answer 38

Torque x (delta) time = (delta) angular momentum

Question 39

From which of Newton's laws is the principle of conservation of angular momentum derived?

Answer 39

Newton's first law

Question 40

How does gravity relate to angular momentum during flight?

Answer 40

When gravity is the only external force acting on an object angular momentum (at take-off) remains constant for the duration of the flight

Question 41

What is the terminology for a combination of rotation and translation (linear motion)

Answer 41

General motion

Question 42

What is an example of how angular momentum about one axis may be transferred to another?

Answer 42

Full twisting one and a half somersault

Question 43

What is an example of a rotation initiated even when total body angular momentum is nil?

Answer 43

Cat twisting in order to land

Question 44

What is the formula for calculating the angular momentum of a [segment] about total body centre of mass?

Answer 44

Equal to: H(Local) - angular momentum of segment about its own centre of mass + H(Remote) - angular momentum of segment about total body centre of mass

Question 45

How is the moment of inertia of a segment of a rotating person calculated?

Answer 45

Moment of inertia of the segment around its own centre of mass + mass of segment x distance from the COM of segment to AXIS OF ROTATION squared