Tension producing torque on a disk

AI Thread Summary
Tension in a string wrapped around a disk can produce torque when the friction between the string and the disk is considered. While tension acts on the string adjacent to the disk, it is the frictional force that generates the torque necessary for rotation. The normal force from the disk on the string does not contribute to torque directly. The key factor is the frictional force multiplied by the radius of the disk, which effectively creates the torque needed to rotate the disk. Understanding these forces is crucial for analyzing systems involving pulleys and rotating disks.
kreutzer
Messages
1
Reaction score
0
When a string is wrapped around a disk and pulled taut to rotate the disk, such as in a pulley, how can tension be the force producing the torque? Tension would only act upon the string next to the disk. I suppose there would be the normal force of the disk on the string, but that wouldn't produce a torque. Is there some other force involved?
 
Physics news on Phys.org
The friction force between string and disk (times the radius) generates the torque.
 

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 'Average velocity as a weighted mean'

Hello everyone, Consider the problem in which a car is told to travel at 30 km/h for L kilometers and then at 60 km/h for another L kilometers. Next, you are asked to determine the average speed. My question is: although we know that the average speed in this case is the harmonic mean of the two speeds, is it also possible to state that the average speed over this 2L-kilometer stretch can be obtained as a weighted average of the two speeds? Best regards, DaTario
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 »

Similar threads

Conservation of Angular Momentum
Replies
9
Views
2K
B Rolling Motion Test: Take the Challenge and Justify Your Answers
Replies
37
Views
4K
I Translational force of a pulley
Replies
27
Views
2K
Angular momentum and centripetal force
Replies
5
Views
6K
Rotational work and forces like static friction and tension
Replies
7
Views
3K
I Understanding the physics of a bosun's chair and mechanical advantage
Replies
6
Views
3K
I Transmission of torque using friction
Replies
32
Views
3K
B The physics of flywheel launchers (like tennis ball shooters)
2
Replies
60
Views
4K
B Rotational Dynamics: Confused about the tension in this string pulling a mass up an incline
Replies
2
Views
1K
Question of Leverage in Rotating Mechanisms
Replies
10
Views
2K

Hot Threads

Recent Insights

Back
Top