KINETICS - moments of inertia

Question 1

in angular kinetics, what is inertia represented by

Answer 1

the mass moment of inertia of an object

Question 2

what is inertia

Answer 2

reluctance of an object to any change in its state of motion
-tendency of objects to keep moving in a straight line at constant velocity

Question 3

how does mass affect inertia

Answer 3

the bigger the mass is, the bigger the force needs to be to produce a given linear acceleration

Question 4

how does inertia affect mass moment of inertia

Answer 4

the bigger the inertia, the bigger the moment needes to be to produce a given angular acceleration

Question 5

how does moment of inertia differ from mass

Answer 5

-not a constant with a non-rigid body
-has diff. values depending on the location of the axis of rotation and the direction
-mass resists linear motion equally in ANY direction

Question 6

as the mass moves farther away from an axis of rotation, what happens to the moment of inertia

Answer 6

it will increase as the square of the displacement

Question 7

moment of inertia increases with what 2 things

Answer 7

increase in mass and increase in distance from the axis of rotation

Question 8

moment of inertia depends on what 4 thigns

Answer 8

-objects mass
-object shape (distribution of mass)
-distance of the axis of rotation from the CoM
-orientation of the axis of rotation

Question 9

what factors affect the distribution of mass about an axis which the body is rotating

Answer 9

body position and axis of rotation

Question 10

what are 2 ways we can estimate a segments mass

Answer 10

-its volume
-DEXA

Question 11

what are 2 ways we can estimate a segments CoM location

Answer 11

-geometric slides
-DEXA

Question 12

how can we estimate a segments moment of inertia

Answer 12

quick release method

Question 13

the sum of all psegments (mass proportion of the segment) values for the whole body must equal what

Answer 13

1

Question 14

what is radius of gyration

Answer 14

perpendicular distance from an axis of rotation of a body, to a point of mass in the body where its moment of inertia is equal to the moment of inertia of the entire body

Question 15

the radius of gyration allows us to what

Answer 15

turn body segments into pendulums making it easier to calculate the moment of inertia of an entire body so we do not have to caluclate the moment of inertia of every particle in a segment

Question 16

what happens to moments of inertia as you move it away from the CoM

Answer 16

it increases
-decreases the closer it is to the CoM

Question 17

moment of inertia about someones CoM is equal to what

Answer 17

their mass x radius of gyration

Question 18

what is the center of percussion

Answer 18

the point at which an impact will cause no shock (reaction force) at the grip or point of suspension

Question 19

what happens to object if force is applied under the CoM and CoP

Answer 19

-translates in opposite direction of rotation by a very small amount
-rotates (big moment of force so feel more in this direction)

Question 20

what happens to an object if force is applied at the CoM

Answer 20

translates only
-CoM feel shock in that net movement direction (same as force)

Question 21

what happens to object if force is applied at its CoP

Answer 21

creates backwards moment of force and forward linear force
-they cancel each other out so no shock in hands

Question 22

where are the CoM, CoP and radius of gyration located relative to each other

Answer 22

-Com of mass neares to the axis of rotation, then the radius of gyration and then CoP furthest from the axis of rotation