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

Torque and Inertia of objects on Inclined plane

  • Thread starter cooltee13
  • Start date
25
0
1. Homework Statement
a block with mass m1= 2 kg, and a block of mass m2 = 6kg are connected by a massless string over a pulley in the shape of a solid disk having radius R = .25m and mass M = 10 kg. These blocks are allowed to move on a fixed wedge of angle pheta = 30 degrees. the coefficent of kinetic friction is .36 for both blocks and pulley. Determine A) the acceleration of the two blocks and B) the tensions in the string on both sides of the pulley.


2. Homework Equations
well, I already solved part A) I just need help with part B. I used the sumTorque = Ialpha, where alpha = a/R. along with this equation below:


3. The Attempt at a Solution
well, i wanted to solve for a so i did the following:(note f=coefficent of friction*): -T1Rf+60cos(T2)Rf = 1/2mR^2*(a/R) ====> -T1f +60cos(T2)f = 1/2ma.

M2gf - T1f + 60cosT2f = 1/2Ma
M2gf = M1af + 60cosM2af + 1/2Ma
M2gf = a(M1f + 60cosM2f + 1/2M)
a = M2gf/(M1f + 60cosM2f + 1/2M) = .31 m/s^2

Im not sure how to solve for the Tension though, do i use the same equation??
 

Answers and Replies

25
0
The answer for B is 7.67 N and 9.22 N.

But I want to know how they got that. Can anybody help please?
 
25
0
can anybody help? do I need to explain more?
 
Doc Al
Mentor
44,827
1,083
A diagram would be helpful. Are both sides of the wedge at an angle of 30 degrees with the horizontal?

In any case, assuming you've correctly found the acceleration, just apply Newton's 2nd law to each block separately to find the tensions.
 
25
0
Im not sure how to put a diagram on this forum, but If i apply newtons second law, I dont end up with the same Tensions as the book answer.

F = ma
I come up with 6.08 N for T1
 
Doc Al
Mentor
44,827
1,083
Show exactly what you did to get the tension. (Until I understand the setup better, I cannot verify your answer for the acceleration.)
 
25
0
how do I insert an image so i can show you the picture?
 
Doc Al
Mentor
44,827
1,083
One of the icons in the post editing window is for inserting images. Or you can attach a file.
 

Related Threads for: Torque and Inertia of objects on Inclined plane

  • Last Post
Replies
15
Views
1K
  • Last Post
Replies
4
Views
196
  • Last Post
Replies
7
Views
1K
  • Last Post
Replies
12
Views
8K
Replies
1
Views
2K
Replies
1
Views
4K
Replies
9
Views
4K
Top