# Homework Help: Mechanism that causes tension and normal force?

1. Oct 17, 2012

### InertialRef

1. The problem statement, all variables and given/known data

What is a mechanism that might cause a rubber band or a string to develop tension in response to a force that you apply?

What mechanism explains how walls and tables exert normal forces without bending noticeably?

2. Relevant equations

None, since this is a conceptual question.

3. The attempt at a solution

I initially wrote down the elasticity of the material used for the rubber band as well as the wall. However, I'm not completely sure my reasoning is correct. Elasticity only affects how much the object would stretch when a force is applied, not the tension force that is developed in response. Even if you had two rubber bands, one more stiffer than the other, if you applied the same amount of force on them, wouldn't they exert the same amount of tension back? In that case then, wouldn't it be the magnitude of the force exerted upon the rubber band or wall that is the mechanism?

2. Oct 17, 2012

### CWatters

I think they are asking for a deeper explanation. For example what stops a rubber band (or anything else) simply falling apart when a force is applied? What keeps the material together?

3. Oct 17, 2012

### InertialRef

I'm not completely sure about that, since it's a first year physics course. But if they were asking for a deeper explanation, wouldn't that involve discussing the types of bonds that make up the material?

4. Oct 17, 2012

### CWatters

May not need to explain the different type of bonds, just that bonds are involved?

The question about walls and tables asks why they don't bend so perhaps this is also a question about tension rather than compression? Otherwise for compression I think you have to talk about the Pauli exclusion principle? But have you covered that yet?