• Support PF! Buy your school textbooks, materials and every day products Here!

Moment of inertia of solid slab

  • Thread starter songoku
  • Start date
  • #1
1,326
44

Homework Statement


Solid slab with moment of inertia 2 kg m2 is given the forces as shown.
1-1.jpg


Find the angular acceleration if θ = 37°, R1 = 10 cm, R2 = 25 cm

Homework Equations


τ = I . α

The Attempt at a Solution


This is what I've tried although I don't know it is correct or wrong; I tried to find all the torques by the 4 forces.
τ1 = 10 x R2 (clockwise)
τ2 = 10 x R1 (anti-clockwise)
τ3 = 20 x R1 (anti-clockwise)

I can't find the fourth torque because I don't know how to find the perpendicular distance from the inclined-10 N force to the center. Please help

Thanks
 

Answers and Replies

  • #2
1,137
0
Hint: You can resolve it into 2 components: tangential and radial
 
  • #3
1,326
44
Hint: You can resolve it into 2 components: tangential and radial
Sorry I don't get it. The arrow of the force is "toward" the slab, not "away" from it so if I resolve the force, I will get 10 cos θ and 10 sin θ but I don't see that one of them is tangential and one of them is radial.
 
  • #4
1,137
0
Sorry I don't get it. The arrow of the force is "toward" the slab, not "away" from it so if I resolve the force, I will get 10 cos θ and 10 sin θ but I don't see that one of them is tangential and one of them is radial.
You are right, one of them wont actually be radial

attachment.php?attachmentid=42453&stc=1&d=1325703328.jpg


But since the blue distance is no given so i assume that its the imperfection of the figure causing the problem.
If you have a way of finding the blue distance the its good or else IMO you can call it radial ...
 

Attachments

  • #5
1,326
44
You are right, one of them wont actually be radial

attachment.php?attachmentid=42453&stc=1&d=1325703328.jpg


But since the blue distance is no given so i assume that its the imperfection of the figure causing the problem.
If you have a way of finding the blue distance the its good or else IMO you can call it radial ...
OK I think I get it. Thanks for your help :)
 

Related Threads on Moment of inertia of solid slab

  • Last Post
Replies
4
Views
3K
  • Last Post
Replies
11
Views
13K
  • Last Post
Replies
2
Views
1K
  • Last Post
Replies
9
Views
3K
  • Last Post
Replies
10
Views
8K
  • Last Post
Replies
4
Views
1K
Replies
5
Views
1K
Replies
4
Views
10K
  • Last Post
Replies
2
Views
3K
Replies
2
Views
2K
Top