What is the tension in the string for two blocks on a spinning turntable?

In summary, two identical blocks tied together with a string are placed on 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 maximum angular frequency for both blocks to not slide is 12.7, and the tension in the string for a mass of 21 g is 17N. The coefficient of static friction is µs = 0.74. However, after converting the mass to kg, the correct tension is found to be 1.7N.
  • #1
rgalvan2
30
0
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+[tex]\mu[/tex]mg=mR1w^2
-T+[tex]\mu[/tex]mg=mR2w^2

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

Help Please!
 
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  • #2
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? :)
 
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  • #3
did u convert grams to kg?
 
  • #4
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
haha yeah, i just solved it thanks to some help from someone else. peace. :)
 

1. What is the purpose of studying blocks on a turntable?

The purpose of studying blocks on a turntable is to understand the principles of rotational motion and how it can affect the behavior of objects placed on a rotating surface.

2. How does the mass of the blocks affect their movement on the turntable?

The mass of the blocks directly affects the rotational inertia of the system, which determines how easily the blocks can be accelerated or decelerated as the turntable rotates.

3. Can the speed of the turntable affect the movement of the blocks?

Yes, the speed of the turntable can affect the movement of the blocks. A higher rotational speed will result in a greater centrifugal force acting on the blocks, causing them to move outward and potentially fall off the turntable.

4. How does friction play a role in the movement of blocks on a turntable?

Friction between the blocks and the turntable surface can either help or hinder the movement of the blocks. If the blocks have a rough surface, they may grip onto the turntable and rotate with it. However, if the surface is too smooth, the blocks may slip and slide, making it difficult to predict their movement.

5. Are there any real-world applications for studying blocks on a turntable?

Yes, understanding rotational motion and the behavior of objects on a rotating surface is important in many fields such as engineering, physics, and even sports. For example, understanding the principles of rotational motion can help engineers design stable structures and athletes improve their performance in sports that involve spinning or rotating movements.

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