How Does a Wall Push Back with Equal Force?

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Homework Help Overview

The discussion revolves around the concept of force and reaction in the context of pushing against different materials, specifically fabric and a wall. Participants explore how these materials respond to applied forces, questioning the underlying principles of potential energy and molecular interactions.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants discuss the analogy between pushing on fabric and a wall, questioning how both materials can exert an equal and opposite force. There is curiosity about the mechanisms that allow the wall to push back without stretching, as well as the role of molecular bonds in these interactions.

Discussion Status

The discussion is active, with participants sharing insights about the nature of forces and material responses. Some guidance is provided regarding the behavior of molecular bonds in both fabric and walls, but there is no explicit consensus on the explanations offered.

Contextual Notes

Participants are operating under the assumption that the forces involved are equal and opposite, as per Newton's third law, and are exploring the implications of this in different material contexts. There is a focus on understanding the physical principles without resolving the underlying complexities fully.

UrbanXrisis
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If a piece of fabric was stretched out, and I pushed my finger into the fabric with a force of 5N, the fabric will push back the 5N because of its potential energy. correct?

So what if I did the the same thing and pushed my finger agaist a wall? The wall doesn't stretch but it still pushs back with 5N. How does it know to puch back 5N on my finger?
 
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hmm, seems to me that if it didnt push back at 5 N it would either throw you back or you would break the wall.
 
hahaha, I never knew I was that strong. Why does the fabric have to stretch to produce the 5N?
 
UrbanXrisis said:
If a piece of fabric was stretched out, and I pushed my finger into the fabric with a force of 5N, the fabric will push back the 5N because of its potential energy. correct?
I assume you are asking: What is going on with the fabric that allows it to push with 5N of force? When you push the fabric, you are stretching the molecular bonds--like little springs--which resist that distortion.

So what if I did the the same thing and pushed my finger agaist a wall? The wall doesn't stretch but it still pushs back with 5N. How does it know to puch back 5N on my finger?
Ah, but the wall compresses. When you push on the wall, you are compressing those molecular "springs" that constitute the surface of the wall.
 
Pretend it's a horizontal spring on a table. If you push on it (horizontally) with a constant force, it will be compressed, but eventually it will push back with enough force to keep your hand in equilibrium. This is because [itex]F_{spring}=-kx[/itex], where x is displacement from equilibrium position. I believe the fabric works the same.
 
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