chapter 7 Flashcards
angular inertia
property of an object to resist changes in its angular motion
moment of inertia quantifies
how an objects mass is distributed relative to a specific axis of rotation
mass farther from the axis creates ___ angular resistance
more
mass closer to the axis creates ___ angular resistance
less
radius of gyration describes
how from from an axis of rotation all the objects mass must be concentrated to create the same resistance to change in angular motion as the object had in its original shape
radius of gyration makes it easier to calculate
moment of inertia
moment of inertia (I) depends on
mass, distribution of mass
double the mass =2 x I
double the gyration=
4xI
implement axis not passing through cg
eccenric axis
what part of the implement does the performer hold
grip/end
eccentric axis new axis called
parallel axis
mass farther from axis of rotation means ___ is greater
moment of inertia
3 principal axes in the human body
AP, transverse, longitudinal
somersault plane and axis
sagittal, ML axis
cartwheel plane and axis
frontal, AP axis
twist plane and axis
transverse, ML axis
altering the relative angle at a joint or joints changes moment of inertia by
changing the mass distribution around a joint axis
angular momentum quantifies
the angular motion of an object
angular momentum describes both
current state of motion, resistance to changing motion
vector quantity needs
magnitude, direction
Ha will change because of changes in
either or both I and w
Ha of body is the sum of
angular momenta of individual segments
angular momentum of an object remains constant unless a
net external torque acts on it
for a rigid projectile, ____ is the only external force
gravity
weight acts through the
cg
weight has no ___ around the cg
moment arm
weight creates no ___ on a projectile
external torque
for faster spin, reduce ___ (arms __)
I, in
for slower spin, increase ___ (arms___)
O, out
repositioning one or more segments of a body must be countered byrepositioning one or more segements in the __ direction, maining constant ___
opposite, Hcg
angularly accelerate=change in
angular momentum
the change in angular momentum of an object is proportional to ____ exerted on it, and the change is in the direction of _____
the net external force, net external torque
if I changes when T is applied, change in ___ is greater
w
