Do I understand this correctly?

[Hyburn]

Homework Statement

the theory behind Parallel axis theorem

Homework Equations

parallel axis theorem:Io=Ig+md²
Radius of Gyration=Ig=m*K²

The Attempt at a Solution

ok folks If I understand this theory correctly the radius of gyration is the radius or distance from the axis of rotation to the center of the AREA

the parallel axis then takes this area into account and converts the equation to account for the area and the mass.

I am trying to teach myself dynamics before I pay for another course at college and bomb out because the professors don't explain anything...

is this a correct understanding? if not can you help me?

 

[Hyburn]

sorry, not center of area, but center of mass

ill need help understanding this as well

-thanks

 

[SteamKing]

Homework Statement

the theory behind Parallel axis theorem

Homework Equations

parallel axis theorem:Io=Ig+md²
Radius of Gyration=Ig=m*K²

The Attempt at a Solution

ok folks If I understand this theory correctly the radius of gyration is the radius or distance from the axis of rotation to the center of the AREA

the parallel axis then takes this area into account and converts the equation to account for the area and the mass.

I am trying to teach myself dynamics before I pay for another course at college and bomb out because the professors don't explain anything...

is this a correct understanding? if not can you help me?

It often helps to know some definitions when trying to teach yourself a subject:

http://en.wikipedia.org/wiki/Radius_of_gyration

Insofar as a connection between the gyradius and the parallel axis theorem, there is only an indirect one.

The PAT is used to calculate the MOI about a different set of axes, given an inertia value about an axis which is parallel. For example, when calculating the MOI of a composite area or mass, we usually want the MOI about the centroid of the combined area or mass. The PAT allows us to make this calculation, using the area or mass, the location of the centroid of each part, and the MOIs of the individual parts.

The gyradius, on the other hand, gives a rough measure of the distribution of mass or area about an axis. A larger gyradius implies that the area or mass is distribued further away from the axis. The gyradius would typically be calculated for a composite area or mass after its MOI about the centroid had been determined.