Explaining Rotational Mechanics: Friction and Stationary Disc

In summary, the conversation discusses the phenomenon of a disc staying stationary when placed on top of a plank and pulled. It is explained that the friction between the plank and disc creates an unbalanced torque, causing the disc to spin. However, this friction should also cause the disc to accelerate, so the question is raised as to why it remains stationary. The assumption that it stays stationary is questioned and it is suggested to apply Newton's law. The conversation then shifts to discussing a book or coaching institute that provides difficult questions.
  • #1
AdityaDev
527
33
When you put o disc on top of a plank and if you pull the plank, the disc rotates but stays stationary.
Here the friction between the plank and disk produces an unbalanced torque and hence it spins.But this friction should also cause an acceleration in the disc right? Then why does it remain stationary?
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  • #2
who gived the assumption that it stay stationary? it does not stay stationary at all i think, just apply Newton's law...i'm curios about answers to this question :)
 
  • #3
GiuseppeR7 said:
who gived the assumption that it stay stationary? it does not stay stationary at all i think, just apply Newton's law...i'm curios about answers to this question :)
Sorry. It doesn't stay stationary. Actually i was thinking about this question. I did not understand it properly.
I got the first two correct but i am still working on Q3.
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  • #4
ah ok :) what book is that by the way? title and author? thanks!
 
  • #5
GiuseppeR7 said:
ah ok :) what book is that by the way? title and author? thanks!
You can't buy it. You have to join my coaching institute. The questions are set by some reputed teachers and the book gets updated every year. No particular author. It's called Grand Masters Package.the questions are very difficult.
 
  • #6
ah ok...thank you :)
 

FAQ: Explaining Rotational Mechanics: Friction and Stationary Disc

1. What is rotational mechanics?

Rotational mechanics is a branch of physics that studies the motion and behavior of objects that rotate around a fixed axis. It involves concepts such as angular velocity, torque, and moment of inertia.

2. How does friction affect rotational motion?

Friction is a force that opposes the motion of an object. In the case of rotational motion, friction can cause a stationary disc to start rotating or slow down a rotating disc. The amount of friction depends on the coefficient of friction between the surfaces in contact and the normal force applied.

3. What is the role of a stationary disc in rotational mechanics?

A stationary disc is often used as a reference point in rotational mechanics. It allows us to analyze the motion of a rotating object in relation to a fixed point. It also helps to calculate the angular velocity and acceleration of the rotating object.

4. How does the mass of a disc affect its rotational motion?

The mass of a disc affects its moment of inertia, which is a measure of an object's resistance to rotation. A disc with a larger mass will have a larger moment of inertia, making it more difficult to rotate. This means that a larger force or torque is required to accelerate or decelerate the disc.

5. What is the difference between static and kinetic friction in rotational mechanics?

Static friction occurs when two surfaces are in contact but not moving relative to each other, while kinetic friction occurs when there is relative motion between the surfaces. In rotational mechanics, static friction can be responsible for causing a stationary disc to start rotating, while kinetic friction can slow down a rotating disc.

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