Conservation of Mechanical Energy Problem

Click For Summary

Discussion Overview

The discussion revolves around a problem involving the conservation of mechanical energy in the context of a swinging motion. Participants explore the concept of breaking tension in a rope as a girl swings from a tree branch, focusing on the forces acting on the rope and the calculations required to determine the minimum breaking tension needed to prevent the rope from snapping.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant expresses confusion about the concept of breaking tension and what calculations are necessary.
  • Another participant suggests that the tension in the rope at the moment of breaking should be zero, prompting further inquiry into this assertion.
  • A different participant assumes that the maximum tension experienced by the rope during the swing must be calculated to determine the required breaking tension, providing an example with hypothetical values.
  • There is a question raised about the forces acting on the rope and whether any work is done during the swing, indicating uncertainty about the dynamics involved.
  • A participant explains that at the bottom of the swing, the girl will have maximum speed and thus maximum tension in the rope, suggesting that conservation of energy can be used to find this speed and the corresponding tension.

Areas of Agreement / Disagreement

Participants do not appear to reach a consensus on the concept of breaking tension or the calculations involved. Multiple viewpoints and uncertainties remain regarding the forces acting on the rope and the application of conservation of energy.

Contextual Notes

There are unresolved questions about the assumptions regarding forces, the definition of breaking tension, and the calculations needed to determine the maximum tension during the swing. The discussion also reflects varying levels of understanding among participants.

Who May Find This Useful

This discussion may be useful for individuals learning about mechanics, particularly those interested in the dynamics of swinging objects and the application of conservation of energy principles in problem-solving scenarios.

smeagol
Messages
6
Reaction score
0
This is something I am learning on my own. However, this problem is confusing me:

Red is a girl of mass m who is taking a picnic lunch to her grandmother. She ties a rope of length R to a tree branch over a creek and starts swing from rest at point A, which is a distance R/2 lower than the branch. What is the minimum breaking tension for the rope if it is not to break and drop Red into the creek?

What is this breaking tension thing? I don't quite understand what I am suppose to calculuate.
 
Physics news on Phys.org
The Tension of the rope at the time of breaking will be zero.

Think why it Should be zero?
 
I'll assume you've already calculated the tension on the rope for all points during red's swing.

What is the maximum value for this tension. Let's say it was 100N.

Now let's say that the breaking tension in the rope was 90N. this means that at 90N or more tension, the rope will snap.

So in order that red not plummet to her icy doom the breaking tension will have to be greater that the largest tension the rope expieriences during the swing.
 
then there's no force pulling on the rope?

Also. How is there anywork done on this? the mass is accelerating toward the center, but movint tangent to the circle?
 
Originally posted by smeagol
What is this breaking tension thing? I don't quite understand what I am suppose to calculuate.
When the girl is at the bottom of the swing, she will have maximum speed and the tension in the string (if it doesn't break!) will be maximum.

You can find her speed at the bottom using conservation of energy.

Since she is moving in a circle, you can calculate what the force must be pulling her towards the center. And thus find what the tension in the rope must be. The "breaking tension" of the rope must be greater than the tension at the bottom, else the rope breaks. Make sense?
 

Similar threads

  • · Replies 9 ·
Replies
9
Views
2K
  • · Replies 77 ·
3
Replies
77
Views
7K
  • · Replies 14 ·
Replies
14
Views
3K
  • · Replies 65 ·
3
Replies
65
Views
6K
Replies
2
Views
2K
  • · Replies 4 ·
Replies
4
Views
3K
  • · Replies 30 ·
2
Replies
30
Views
3K
  • · Replies 11 ·
Replies
11
Views
3K
  • · Replies 6 ·
Replies
6
Views
4K
  • · Replies 22 ·
Replies
22
Views
3K