LECTURE #19 - angular kinetics (2)

Question 1

what does angular motion refer to ?

Answer 1

rotation about a point

Question 2

when does angular motion occur ?

Answer 2

when a force acts about a distance from a fixed point

Question 3

what does angular kinetics refer to ?

Answer 3

the branch of mechanics that deals with the causes of angular motion

Question 4

what is inertia ?

Answer 4

the property of an object that resists change in motion

Question 5

what is linear inertia quantified as ?

Answer 5

an objects mass

Question 6

what is angular inertia ?

Answer 6

the property of an object to resist changes in its angular motion

Question 7

what is mass ?

Answer 7

measure of object’s inertia or resistance to change in acceleration

Question 8

what is moment of inertia = ?

Answer 8

object’s resistance to a change in a angular acceleration

Question 9

moment of inertia depends on what two factors ?

Answer 9

mass and distribution of mass relative to axis of rotation

Question 10

TRUE OR FALSE

in the human body masses cannot be concentrated into single points (non-symmetrical body parts)

Answer 10

TRUE

Question 11

what is radius of gyration (k) ?

Answer 11

the distance that represents how far away from the axis of rotation a body’s mass is distributed

Question 12

COM vs. Radius of Gyration ; what is centre of mass ?

Answer 12

point where gravitational force is applied (the balance point)

Question 13

COM vs. Radius of Gyration ; what is radius of gyration ?

Answer 13

• distance mass is distributed from a specific axis of rotation
• point where mass can conceptually be concentrated such that it does not alter the moment of inertia (I)

Question 14

TRUE OR FALSE

rotation can not occur about different axes

Answer 14

FALSE

rotation can occur about different axes

Question 15

TRUE OR FALSE

each axis has its own moment of inertia

Answer 15

TRUE

Question 16

TRUE OR FALSE

each axis shares the same moment of inertia

Answer 16

FALSE

each axis has ITS OWN moment of inertia

Question 17

FILL IN THE BLANK

the _______ mass is distributed to the axis of rotation, __________ it is to rotate

Answer 17

the CLOSER mass is distributed to the axis of rotation, EASIER it is to rotate

Question 18

how many principal axes does the human motion occur about ?

Answer 18

3

Question 19

what are the three axes for human motion ?

Answer 19

• transverse
• frontal
• longitudinal

Question 20

linear momentum is the product of what ?

Answer 20

mass and velocity

Question 21

for the formula M = mv, what does M quantify ?

Answer 21

the linear motion of an object

Question 22

what is angular momentum the angular analog of ?

Answer 22

angular momentum is the angular analog of linear momentum

Question 23

what is angular momentum a product of ?

Answer 23

body’s rotational inertia and rotational velocity about an axis

Question 24

TRUE OR FALSE

angular momentum is a vector quantity

Answer 24

TRUE

Question 25

TRUE OR FALSE

direction is same as the angular velocity it defines ?

Answer 25

TRUE

Question 26

does angular momentum have magnitude and direction ?

Answer 26

YES

Question 27

what is the conservation of angular momentum ?

Answer 27

declares that the angular momentum of an isolated system will remain the same regardless of any movements or torques that are produced internal to the system. as long as no external toque is applied to the system

Question 28

what is newtons first law ?

Answer 28

law of inertia

Question 29

define the law of inertia :

Answer 29

any given system will continue to move with constant momentum unless an external force acts to change that momentum

Question 30

what is newtons second law ?

Answer 30

law of acceleration

Question 31

define the law of acceleration :

Answer 31

• the change in angular momentum of an object is proportional to the net external torque exerted on it , and this change is in the direction of the net external torque
• the net external torque is proportional to the rate of change in angular momentum the change in

Question 32

what is newtons third law ?

Answer 32

angular analog / law of reaction

Question 33

define angular analog / law of reaction :

Answer 33

for every torque exerted by one body on another body, there is an equal and opposite torque e exerted by the second body on the first

Question 34

TRUE OR FALSE

torque generated by one body part to rotate that part results in a counter-torque by another body part (opposite direction)

Answer 34

TRUE