Work done by varying friction against a constantly moving surface

AI Thread Summary
A metal disk spins at a constant rate of one cycle per second, with a small metal block pressed against it at a radius of four inches. The friction coefficient between the disk and block is 0.1, and a time-varying force is applied to the block arm to manipulate the normal force. The friction is maintained consistently, likely due to the surface finish or lubrication. The work done by the block arm against any resistance is proportional to the normal force applied. This understanding aligns with the principles of work in physics.
jamesadrian
Messages
32
Reaction score
2
Suppose a metal disk is spinning at constant rate of one cycle per second and at a radius of about four inches a small metal block is pressed against the disk. The circumference of the path of the contact is exactly one foot.

The coefficient of kinetic friction between the disk and the small metal block is .1 and the small metal block is attached to an arm (the block arm). The other end of the block arm is attached with a bearing to the center of rotation of the disk.

A time-varying force is applied to the block arm so as to manipulate the force between the disk and the small metal block. This force follows the arm wherever it goes and we need not be concerned about where the force comes from. The direction of this force is into the face of the disk (at a right angle to the surface of the disk, or the normal).

The coefficient of kinetic friction is kept extremely constant, possibly because of the polish of the metal or possibly because of a special lubricant.

If anything opposes the rotation of the block arm, the work (force times distance) that can be done by the block arm against this resistance would seem to be proportional to the normal force applied by the block arm.

Do I have this right?

Thank you for your help.

Jim Adrian
 
Physics news on Phys.org

Thread '1:1 versus 2:1 Mechanical Advantage debate'

The rope is tied into the person (the load of 200 pounds) and the rope goes up from the person to a fixed pulley and back down to his hands. He hauls the rope to suspend himself in the air. What is the mechanical advantage of the system? The person will indeed only have to lift half of his body weight (roughly 100 pounds) because he now lessened the load by that same amount. This APPEARS to be a 2:1 because he can hold himself with half the force, but my question is: is that mechanical...
View full post »

Thread 'Newton's first law?'

Some physics textbook writer told me that Newton's first law applies only on bodies that feel no interactions at all. He said that if a body is on rest or moves in constant velocity, there is no external force acting on it. But I have heard another form of the law that says the net force acting on a body must be zero. This means there is interactions involved after all. So which one is correct?
View full post »
Thread 'Beam on an inclined plane'

Thread 'Beam on an inclined plane'

Hello! I have a question regarding a beam on an inclined plane. I was considering a beam resting on two supports attached to an inclined plane. I was almost sure that the lower support must be more loaded. My imagination about this problem is shown in the picture below. Here is how I wrote the condition of equilibrium forces: $$ \begin{cases} F_{g\parallel}=F_{t1}+F_{t2}, \\ F_{g\perp}=F_{r1}+F_{r2} \end{cases}. $$ On the other hand...
View full post »

Similar threads

I Work-Energy Theorem for Moving Block and Spring System?
Replies
4
Views
2K
B Rolling Motion Test: Take the Challenge and Justify Your Answers
Replies
37
Views
4K
I How to flatten the surface of a viscous gel?
Replies
7
Views
2K
I Transmission of torque using friction
Replies
32
Views
3K
Friction on a flat rotating surface
Replies
4
Views
4K
Finding the work done by a block
Replies
4
Views
3K
Does work energy theorem fail while dealing with friction?
Replies
6
Views
3K
Non-conservative work energy theorem and potential energy
Replies
3
Views
2K
Why is the work done double its expected value? (conveyer belt)
2
Replies
58
Views
5K
Clarification on force on frictional surface constant speed
Replies
1
Views
2K

Hot Threads

Recent Insights

Back
Top