Kinetics: Moment of Inertia

every concept in linear kinetics has an

analogue in angular kinetics

define inertia

reluctance of any physical object to any change in its state of motion

the tendency of objects to keep moving in a straight line at constant velocity is

inertia

inertia is described by which of newton’s laws

1st

greater mass = greater force to produce a given

linear acceleration

how does moment of inertia differ from mass

it is not a constant with a non-rigid body

moment of inertia differs from mass in that it has different values depending on the location of the

axis of rotation

moment of inertia differs from mass in that it has different values depending on the direction of

axis of rotation

mass resists linear motion equally in ____ direction

any

in inertia, the effect of changing length is greater than changing the

mass of the object

when you change the mass, the ____ changes as well

inertia

in the equation I=mr, what is r

distance of particle from axis of rotation (radius)

what is inertia measured in

kg.m2

as the mass moves farther from an axis of rotation, the moment of inertia will (increase/decrease) as the square of the displacement

increase

Inertia increases with

greater mass

greater distance from axis of rotation

moment of inertia will always be greater in what plane?

sagittal ; x plane

how do we estimate a segment’s mass

DEXA

how to we estimate a segment’s center of mass location

geometric solids or DEXA

how do we estimate moment of inertia

quick release method

in Dempster’s body segment parameter, lower case and upper case letters mean what?

lower = individual to the person

upper proportions relative to table

in Dempster’s body segment table, the sum of all P values must equal

1

define radius of gyration

point mass located that turns a body segment into pendulum

the distance between an axis and a point (mass) in space

we typically calculate the moment of inertia about a segment’s center of

mass (Icg)

centre of percussion definition

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

______ is nearest to the axis of rotation

center of mass

_______ is past the center of mass

radius of gyration

_______is past the radius of gyration

center of percussion