Radius of Gyration?

  • Thread starter theBEAST
  • Start date
  • #1
364
0

Homework Statement


TzlCO.png


The Attempt at a Solution


Alright, so the solution manual shows that the intertia of the disk is:
I = m * k2, where k is the radius of gyration​

However why can't the inertia of the disk be:
I = 0.5 * m * r2, where r is the radius of the disk​
This is the formula for the inertia of a rotating disk... However when I plug in all my numbers I get a different inertia value when compared to the inertia value that I got using the radius of gyration.
 

Answers and Replies

  • #2
haruspex
Science Advisor
Homework Helper
Insights Author
Gold Member
2020 Award
36,728
7,078
Because the spool is not a uniform disk. You don't need to know why it's not uniform, just accept that you are given the effective radius.
 
  • #3
364
0
Because the spool is not a uniform disk. You don't need to know why it's not uniform, just accept that you are given the effective radius.

Ah okay, I wish it said that the density is not uniformly distributed... But thanks!
 

Related Threads on Radius of Gyration?

  • Last Post
Replies
1
Views
4K
  • Last Post
Replies
1
Views
4K
  • Last Post
Replies
4
Views
11K
  • Last Post
Replies
2
Views
12K
Replies
6
Views
3K
Replies
3
Views
2K
Replies
10
Views
4K
Replies
10
Views
2K
Top