People lifting themselves with simple fixed pulley

Click For Summary

Discussion Overview

The discussion revolves around the feasibility of people lifting themselves using a simple fixed pulley system, exploring both theoretical and practical aspects of the scenario. Participants question the mechanics involved and seek demonstrations or calculations to verify their claims.

Discussion Character

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

Main Points Raised

  • One participant expresses skepticism about the practicality of the pulley system, questioning how individuals can remain on the platform without being "glued" to it.
  • Another participant suggests that the pressure from the person's weight on the platform is sufficient for the system to work, indicating that glue is unnecessary.
  • A different viewpoint reiterates the initial skepticism, asking for clarification on what "won't work" means in this context.
  • Some participants propose that for the system to function, the combined weight of the individuals must exceed that of the platform.
  • One participant introduces an alternative method of using a rope over a tree branch, suggesting that a platform may not be necessary at all.
  • Another participant warns about safety concerns when using a rope system and suggests a small model for demonstration purposes.
  • A participant invites others to provide numerical examples, including specific weights and forces, to analyze the situation mathematically and draw diagrams of the forces involved.

Areas of Agreement / Disagreement

Participants do not reach a consensus; there are multiple competing views regarding the feasibility and mechanics of the pulley system, with some expressing skepticism and others providing alternative methods or conditions under which the system might work.

Contextual Notes

Some assumptions are not explicitly stated, such as the physical capabilities of the individuals involved and the specific setup of the pulley system. The discussion also lacks numerical data to support claims about forces and weights.

REVIANNA
Messages
71
Reaction score
1
I can't convince myself that the situation in this picture is possible in reality though I know the physics works.
I feel that it won't work as the workers are not glued to the platform
can anyone find a demonstration to verify it .please (I'v searched youtube as much as I could)
people lifting themselves with simple fixed pulley (single person will also do)
problems_MIT_rayyan_Physics801_Figures_Pulley_Platform.png
 
Physics news on Phys.org
Why would you need glue if there is half the body weight as pressure between the person and the platform?
 
REVIANNA said:
I can't convince myself that the situation in this picture is possible in reality though I know the physics works.
I feel that it won't work as the workers are not glued to the platform
can anyone find a demonstration to verify it .please (I'v searched youtube as much as I could)
people lifting themselves with simple fixed pulley (single person will also do)
problems_MIT_rayyan_Physics801_Figures_Pulley_Platform.png
There's no need to be glued on the platform. Imagine both persons hold their ropes and suddenly put their knees to the breast. The weight of the persons will lift the platform till both "sit" on it. Afterwards they could grab the rope at a point closer to the ceiling, by alternatley moving one hand above the other and keeping the tension in the rope with fixed hand while standing up (if they are physically strong enough).
 
REVIANNA said:
I feel that it won't work as the workers are not glued to the platform
What do you mean exactly by "it won't work"? What do you think will happen, if they are not glued to the platform (assuming they are heavier than the platform)?
 
Since no numbers are provided, in order for it to work, we need to assume the weight of the people is greater than the weight of the platform.
 
You don't even need a platform for this to work.
You can pull yourself up with a rope thrown over a tree branch. You just make a little loop at one end so you put for foot through it and pull the other end of the rope.
Look up "tree house elevator" to see more sophisticated contraptions, with multiple pulleys.
 
nasu said:
You can pull yourself up with a rope thrown over a tree branch. You just make a little loop at one end so you put for foot through it and pull the other end of the rope.
Careful, we don't want to the OP to hang her/himself. A small model with a basket and a weight would suffice.
 
put some numbers into the question. Look at 1 person of mass 70kg (W = 686N) standing on a platform of mass 20kg (weight = 196N)...he pulls with a force of 400N on the rope...can you calculate what is happening? the acceleration? can you draw a diagram showing the forces acting on the person and on the platform and on the rope??
 

Similar threads

  • · Replies 69 ·
3
Replies
69
Views
17K
  • · Replies 46 ·
2
Replies
46
Views
33K
Replies
4
Views
2K
  • · Replies 5 ·
Replies
5
Views
6K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 27 ·
Replies
27
Views
11K
  • · Replies 26 ·
Replies
26
Views
7K
  • · Replies 7 ·
Replies
7
Views
3K
  • · Replies 5 ·
Replies
5
Views
3K
  • · Replies 5 ·
Replies
5
Views
3K