# Homework Help: Blocks on a Turntable

1. Sep 21, 2008

### rgalvan2

Two identical blocks are tied together with a string and placed along the same radius of a turntable that is spinning about its center. The inner block is 4 cm from the center and the outer block is 5 cm from the center. The coefficient of static friction between the turntable and the blocks is µs = 0.74, and the string is taut.

a) What is the maximum angular frequency such that neither block slides?
I got w= 12.7 which was right

b) Now suppose that the blocks each have a mass m = 21 g. For the value of w you just found, what is the tension in the string?
T= ?N

I am stuck on b) I have 2 eqns:
T+$$\mu$$mg=mR1w^2
-T+$$\mu$$mg=mR2w^2

So I keep getting 17N each time I try. What am i doing wrong?
T=mR1w^2-$$\mu$$mg
=21x.05x12.7^2 - .74x21x9.81
=169.4-152.4= 17N

2. Sep 22, 2008

### CaptainSFS

I can't help you dude. I need help with the same problem. All I can figure out is that the net force points to the center of the circle I believe, and https://www.physicsforums.com/latex_images/18/1883140-2.png [Broken] probably doesn't point toward the center, I think.

I'm still stuck on A and have no idea how to procede.
If you finish the problem, and if you have some extra time could you help me with it please? :)

Last edited by a moderator: May 3, 2017
3. Sep 22, 2008

### CaptainSFS

did u convert grams to kg?

4. Sep 22, 2008

### rgalvan2

I was actually just doing that as when i saw i got a new reply. I thought i tried that before but i must have miscalculated. i got it right now thanks!

5. Sep 22, 2008

### CaptainSFS

haha yeah, i just solved it thanks to some help from someone else. peace. :)