Elasticity of metals springs and rubber bands

In summary, both a spring and rubber band are elastic because they have the ability to reform from deformation and return to their original shape. The elasticity of an object depends on its ability to return to its original shape after being stretched or compressed. While springs work due to normal force, it is the electrical bonds between atoms or molecules that allow rubber bands to snap back to their original position. When an object is strained, it develops internal stress, which can be released, dissipated, or a combination of both. The effect of elasticity when a ball is struck with the same force but with different impact surface areas is not a simple concept and depends on various factors such as contact time and dissipation. Equations such as .5 * K * X
  • #1
Skhandelwal
400
3
How come both spring and rubber band are elastic whereas spring are contracted and rubber bands are stretched? I understand that elasticity of an object depends on it ability to reform from deform. I also get that spring works b/c of normal force(too much contraction...right?-being the reason for rebound) But what does a rubber band works on that makes it snap back to its original position?(what force propels it?)

Thanks.
 
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  • #2
Both the spring and the rubber have the tendency to return to the original shape after being either stretched or compressed. If you didn't realize that fact about compressing rubber then you forgot about bouncing a rubber ball.

In a solid the bonds between neighboring atoms or molecules are visualized like an array of springs in three dimensions, like in a mattress. The bonds are electrical. When the material is stretched or compressed the network of bonds is distorted into a shape that's unstable. It finds equilibrium as it returns to the original shape.
 
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  • #3
Skhandelwal said:
How come both spring and rubber band are elastic whereas spring are contracted and rubber bands are stretched? I understand that elasticity of an object depends on it ability to reform from deform. I also get that spring works b/c of normal force(too much contraction...right?-being the reason for rebound) But what does a rubber band works on that makes it snap back to its original position?(what force propels it?)

Thanks.

When an object is strained, it develops internal stress. The stress energy stores the energy of deformation and can be released (elastic deformation), dissipated (plastic deformation), or some combination of the two (viscoelasticity, viscoplasticity, creep, etc. etc.). The relationship between stress and strain is properly a 4-th rank tensor, but that usually gets simplified considerably by taking into account various material invariances- crystal structure, isotropy, etc.
 
  • #4
Andy please could you provide a comment on the effect of elasticity when a ball is struck with the same force but with objects of different impact surface areas. Does the smaller impact surface area not poke into the ball further than the larger impact surface area. If this is the case would the ball not get greater potential energy from the smaller impact area based on the equation .5 * K * X * X where X=distance of displacement ( ie the distance that the impact area projects into the ball)

Many Thanks

Lucio
 
  • #5
I don't understand what you are asking. Elasticity is a material property, not a property of an interaction.
 
  • #6
Clarification of question

Andy thanks for taking the time to respond.

My basic question is this. If a spherical inflated ball (with a standard inner rubber ball which holds the air and a outer casing of either rubber/leather/plastic) were projected towards a flat surface and then projected at the same speed towards a ridged surface would the ball rebound with more speed from the ridged surface. My observation is that a ball rebounding from a ridged surface seems to be punched back at a greater pace than the ball rebounding from a flat surface. Not knowing the physics of elasticity to any depth, my thoughts were that the ball on striking the the ridged surface has the ridges poke deeper into the ball than the flat surface and therefore the elastic properties of the ball produce a greater elastic effect.

Many thanks for any guidance.

Lucio
 
  • #7
That may be true; the ridges act to decrease the contact area between sphere and wall, so the local deformation may be greater. Contact time and dissipation may be higher as well, though, so it's not clear if there is a single result that would occur.
 
  • #8
Thanks Andy. If contact time and dissipation are higher does that increase the energy of the ball's rebound?

Also, which physics equations would apply when quatifying this effect?

Thanks again
 
  • #9
If the contact time increases, the dissipation also increases, so the stored elastic deformation energy deceases.

As for equations... nothing simple enough for me to write here. Landau and Lif****z's "Theory of Elasticity" is ok, but doesn't take the correct viewpoint, IMO. Better are books like Green and Zerna's "Elasticity" or Marsden and Hughes "Mathematical foundations of elasticity" and the like which take a continuum approach.
 

1. What is elasticity and how does it relate to metals, springs, and rubber bands?

Elasticity is the ability of a material to deform when a force is applied to it and then return to its original shape once the force is removed. Metals, springs, and rubber bands are all materials that exhibit elasticity, meaning they can be stretched or compressed and then return to their original shape.

2. What factors affect the elasticity of metals, springs, and rubber bands?

The elasticity of these materials is affected by factors such as their composition, temperature, and the amount of force applied. Different materials have different levels of elasticity, with some being more flexible and others being more rigid.

3. How does the elasticity of metals, springs, and rubber bands impact their uses?

The elasticity of these materials is crucial for their various uses. Metals with high elasticity, such as steel, are used in construction and manufacturing to withstand heavy loads and stresses. Springs and rubber bands, which have high elasticity, are used in a variety of applications such as in clothing, vehicles, and toys.

4. Can the elasticity of metals, springs, and rubber bands be changed?

Yes, the elasticity of these materials can be altered through various methods. For example, metals can be heat-treated to increase or decrease their elasticity. Springs and rubber bands can be manufactured with different materials or adjusted in their design to change their elasticity.

5. What happens when the elasticity of a material is exceeded?

When the elasticity of a material is exceeded, it can result in permanent deformation or breakage. This is why it is important to consider the maximum elasticity of a material when using it in different applications. Exceeding the elasticity limit of a material can also lead to safety hazards, as the material may not be able to withstand the applied force and could fail catastrophically.

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