Why does adding 1 meter to a rope around the Earth create slack?

  • Context: High School 
  • Thread starter Thread starter LAF
  • Start date Start date
  • Tags Tags
    Perimeter Radius
Click For Summary

Discussion Overview

The discussion revolves around the concept of adding length to a rope wrapped around a spherical object, specifically the Earth, and the resulting slack that occurs. Participants explore the implications of this scenario, questioning intuitive understandings and engaging in a playful examination of the problem.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Homework-related

Main Points Raised

  • One participant describes a hands-on approach using a twine around a sphere to illustrate the concept of slack when adding length to the rope.
  • Another participant expresses that the problem seems more like homework help rather than a brain teaser and provides what they consider a full answer.
  • Some participants reflect on the nature of the problem, suggesting it challenges common sense and expressing disappointment in the perceived lack of engagement.
  • A playful twist is introduced regarding what kind of animal could pass through the slack created by the added length of the rope, with various suggestions made, including ants, bacteria, cats, and bunnies.

Areas of Agreement / Disagreement

Participants do not appear to reach a consensus on the nature of the problem or its implications. There are competing views on whether it is a brain teaser or a straightforward homework question, and differing opinions on the appropriateness of the answers provided.

Contextual Notes

Some assumptions about the nature of slack and the physical properties of the rope and sphere may not be fully articulated, and the discussion does not resolve the mathematical implications of the scenario.

Who May Find This Useful

Individuals interested in conceptual physics, mathematical reasoning, or those looking for playful explorations of common sense challenges may find this discussion engaging.

LAF
Messages
31
Reaction score
0
First, try to use your own sense.

Take a twine (rope) and put it around a ball, or an orange (sphere).
Now you have the circumference (perimeter) of that sphere.
Take this twine and add 1m more (one more meter - it can be any unit of liner measure).
Put this one meter longer twine around the ball again, keeping it equidistant of the surface (circular orbit, ring).
The twine is aprox. 0,159m of the surface of the ball.

Take a twine (rope) and put it around the Earth equator (sphere).
Now you have the circumference (perimeter) of that sphere.
Take this twine and add 1m more (one more meter - it can be any unit of liner measure).
Put this one meter longer twine around the Earth equator again, keeping it equidistant of the surface (circular orbit, ring).
The twine is aprox. 0,159m of the surface of the earth.

Why does it hapen like this?
 
Physics news on Phys.org
LAF said:
Why does it hapen like this?

I put the answer is spoiler tags, but this doesn't seem like a brain teaser, more like a homework help. Even so, I give the full answer.

Because the radius is a linear function of the circumference: r = c / 2pi
As a result, if you add 1 meter to the length of the rope (that is, to the circumference) then you will add 1 / 2pi (approx .159 meter) to the radius regardless of the original length.
 
It´s been boring here and I just tried to show something that breaks the common sense.
Now I see I didn´t. I´ll try harder next time...
 
LAF said:
It´s been boring here and I just tried to show something that breaks the common sense.
Now I see I didn´t. I´ll try harder next time...

You have spoiled the problem. The original one is:
Take a rope and tie it tightly around the Earth. Then add 1 meter to the rope. There will be some slack. What kind of animal will pass through the slack?
Intuitively people will say an ant or even a bacterium (I know a bacterium is not an animal, but people say it).
The real answer would be a cat or a bunny.
 
CEL said:
You have spoiled the problem. The original one is:
Take a rope and tie it tightly around the Earth. Then add 1 meter to the rope. There will be some slack. What kind of animal will pass through the slack?
Intuitively people will say an ant or even a bacterium (I know a bacterium is not an animal, but people say it).
The real answer would be a cat or a bunny.

Your way is much better! Thanks.
 

Similar threads

Graduate Gravity effects on a solid rigid ring around earth
  • · Replies 51 ·
2
Replies
51
Views
9K
Writing: Input Wanted Generation Ship SFV Exodus: Revised Designs
  • · Replies 52 ·
2
Replies
52
Views
8K
Graduate Ball Lightning Debunk, New Proposal
  • · Replies 1 ·
Replies
1
Views
5K
Undergrad How does adding 100 cm to a rope around the Earth affect its radius?
  • · Replies 6 ·
Replies
6
Views
3K
Undergrad Modeling the effects of GW and the "Earth Frame"
  • · Replies 66 ·
3
Replies
66
Views
7K
Writing: Read Only What Does Great Lakes Earth Look Like from Space?
  • · Replies 1 ·
Replies
1
Views
4K
Graduate Astrophysics project gone wrong: why isn't the moon tearing the Earth apart?
  • · Replies 4 ·
Replies
4
Views
4K
Kerbal Space Program - Efficient Launch into Orbit
  • · Replies 5 ·
Replies
5
Views
13K
Earthing & Lightening Protection for a Home on a Mountain Top
  • · Replies 9 ·
Replies
9
Views
10K
Kerbal Space Program - Duna Rocket Launch
  • · Replies 3 ·
Replies
3
Views
5K