Torque and Forces in Spool Movement: Solving for Net Torque and Static Friction

  • Thread starter jaewonjung
  • Start date
  • Tags
    Rolling
  • #1
jaewonjung
9
0
Homework Statement
Problem in picture
Relevant Equations
Fnet=ma
Forces in the x direction: static friction left=Tcostheta to the right
Forces in the y direction: W= Normal force + Tsintheta
Net torque: rTcostheta-RFs=0

Fs=Tcostheta,
rTcostheta-R(Tcostheta)=0
rTcostheta=RTcostheta
r=R

Please help
 

Attachments

  • Screen Shot 2019-04-10 at 5.10.36 PM.png
    Screen Shot 2019-04-10 at 5.10.36 PM.png
    9.1 KB · Views: 256
Physics news on Phys.org
  • #2
This is a multiple choice question, so try to use intuition about rolling vs slipping to eliminate answers. Look at each variable in turn: for instance what if r=R? Will it roll? Then think about theta...what if it is zero...90deg...
 
  • #3
jaewonjung said:
Net torque: rTcostheta-RFs=0
Looks like you are taking moments about the centre of the cylinder. Think again about the torque due to T. Maybe draw a nice big picture, carefully.
(There is a better choice of axis for this problem.)
 
  • #4
I solved it! The torque of the Tension is just Tr, not Trcostheta. Thanks for the help!
 
  • #5
jaewonjung said:
I solved it! The torque of the Tension is just Tr, not Trcostheta. Thanks for the help!
Good.
Note that if you take moments about the point of contact with the ground instead it becomes a matter of simple geometry.
 

Similar threads

Replies
9
Views
2K
Replies
90
Views
4K
Replies
11
Views
932
Replies
5
Views
1K
Replies
4
Views
1K
Replies
25
Views
1K
Replies
97
Views
4K
Back
Top