Chapter 7 - Angular Kinetics Flashcards
(6 cards)
What is inertia?
property of an object that resists changes motion
What is angular inertia? Units and symbol?
property of an object to resist changes in its angular motion
I
units: kg.m^2
*how hard it is to start or stop spinning
What affects angular inertia?
1) mass: more mass = more resistance to change like linear inertia
2) Where the mass is located relative to the axis of rotation
- The farther the mass from the axis, the greater the moment of inertia
- if mass is spread out, intertia is higher
- if mass is closer to the axis, inertia is lower
What is moment of inertia? (I). What are the formula?
quantity that describes angular inertia
I=β(mi)(ri)^2
m - mass
r = perpendicular distance from the axis of rotation
or
πΌπ = πππ 2
Ka = radius of hyration
- βif the entire mass were at distance k from the axis, it would spin the same wat as the real objectβ
K - depends on mass distribution
β
What are principal axes?
What is an example of a principal axis in sports?
special direction about which the moment of inertia is maximized, minimized, or remains constant for rotation
*if you spin an object about a principal axis, it will rotate smoothly
*if you spin it about some other axis, it might wobble or precess
Figure skating:
Longitudinal axis spin when a skater pulls thier arms in they reduce their momnet of inertia and spin faster
Principal axis: longitudinal
What happen to moment of inertia when the length increase?
Moment of inertia increase
I=β(mi)(ri)^2 or I=mr^2
Increasing the distance (r) from the axis causes squared increase in moment of inertia
