Circular Motion: Find Tension at Top of 1.11kg Disc

Click For Summary

Homework Help Overview

The discussion revolves around a problem involving circular motion, specifically calculating the tension in a disc being whirled in a vertical circle. The mass of the disc is 1.11 kg, and it has a radius of 0.680 m with a speed of 8.76 m/s at the top of the circle.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the forces acting on the disc at the top of the circle, including tension and gravitational force. There is an exploration of the relationship between centripetal force and these forces, with some questioning the nature of centripetal force itself.

Discussion Status

The discussion is ongoing, with participants offering insights into the forces involved and suggesting the use of free body diagrams for better understanding. There is an acknowledgment of the need to clarify the definitions and roles of forces in circular motion.

Contextual Notes

Some participants note the importance of recognizing that centripetal force is not a distinct force but rather a term representing mass times acceleration. There is also a mention of the original poster's incorrect attempt at calculating the centripetal acceleration.

electricheart
Messages
6
Reaction score
0

Homework Statement



A 1.11 kg disc is whirled in a vertical circle with radius 0.680m about a fixed point. Find the tension at the top if the speed at the top is 8.76 m/s.

Homework Equations



F= ma
F= m* Acp
Acp= m(w^2*r)

3. The Attempt at a Solution
I figured centripetal force was acting on the mass so I used the equation w=v/r to find omega(w), then I found the Acp. But that answer is incorrect. If at the top of a circle will the tension be the same Acp.
 
Physics news on Phys.org
At the top of the circle, the forces acting are the normal reaction of the 1.11kg mass and the tension. Both acting downwards. The resultant of those two is the centripetal force mv2/r
 
So F + M g = Acp.
Alright, thanks.
 
Centripetal force is not really a force at all, it is a mass*acceleration term.

You will get a much better understanding of this problem (as opposed to simply getting an answer quickly) if you draw a free body diagram and write Sum F = m*a where you recognize that for a body in uniform circular motion, a = - r * omega^2 * er, a vector pointing towards the center of the circle.
 

Similar threads

  • · Replies 8 ·
Replies
8
Views
2K
  • · Replies 4 ·
Replies
4
Views
1K
Replies
19
Views
3K
Replies
7
Views
3K
Replies
11
Views
3K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 9 ·
Replies
9
Views
2K
Replies
8
Views
2K
Replies
2
Views
2K