# Mechanism of mechanical transverse wave in solids

• vcsharp2003
In summary: The case with liquids and gases is that liquids and gases don't have that much shear strength. Transverse waves need a medium rigid enough to propagate, which liquids and gases can't provide.So, it seems there is no restoring force like tension in a rope or surface tension on liquid surface, that can pull back a perpendicularly displaced part of the medium. The rope tension or the surface tension provide the restoring force as well as a force to displace perpendicularly the next part of the rope or liquid. That is why a transverse wave can exist on the surface of a pond but not deep underwater.
vcsharp2003
Homework Statement
Why does a solid medium allow transverse wave to propagate through it?
Relevant Equations
None
I am not sure, but below is my attempt.

In solids the force between adjacent atoms/molecules is very strong. So, when a part of the solid medium is displaced perpendicular to the solid medium like a rope, the atoms/particles in the medium just ahead of the displaced part will tend to bring the displaced part back to its original equilibrium position. At the same time, due to Newton's Third Law, the displaced part will exert an equal and opposite force on the part just ahead of it; consequently, the part ahead will start to move in direction of displaced part.

Thus, we see two things happening.
1. displaced part of medium starts moving towards its original position
2. the part of medium just ahead of displaced part starts moving

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Looks ok to me, except that you mean perpendicular to the direction of travel of the wave.

vcsharp2003
haruspex said:
Looks ok to me, except that you mean perpendicular to the direction of travel of the wave.
Yes, displacement is perpendicular to direction of wave travel.

Also, could I say that transverse mechanical waves cannot exist in liquids and gases because the force between adjacent atoms/molecules is weak so that displaced part of such a medium cannot be pulled back to its equilibrium position by adjacent atoms/molecules? Or there is something else happening in liquid or gaseous medium.

Edit: Probably, forces that restore original position of atom/molecule is completely absent in liquids and gases.

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vcsharp2003 said:
Yes, displacement is perpendicular to direction of wave travel.

Also, could I say that transverse mechanical waves cannot exist in liquids and gases because the force between adjacent atoms/molecules is weak so that displaced part of such a medium cannot be pulled back to its equilibrium position by adjacent atoms/molecules? Or there is something else happening in liquid or gaseous medium.

Edit: Probably, forces that restore original position of atom/molecule is completely absent in liquids and gases.
The term you are looking for is "shear force".

hutchphd and vcsharp2003
vcsharp2003 said:
Also, could I say that transverse mechanical waves cannot exist in liquids and gases...
"Transverse waves cannot propagate in a gas or a liquid because there is no mechanism for driving motion perpendicular to the propagation of the wave."

http://hyperphysics.phy-astr.gsu.edu/hbase/Sound/tralon.html

haruspex said:
The term you are looking for is "shear force".
So, is the presence of shear force in liquids and gases responsible for perpendicularly displaced sections of medium to not come back to original position?
Shear force seems to be a force parallel to the plane being cut/sheared. It seems to prevent elasticity by exerting a force pointing away from equilibrium position of the displaced part.

Lord Jestocost said:
"Transverse waves cannot propagate in a gas or a liquid because there is no mechanism for driving motion perpendicular to the propagation of the wave."

http://hyperphysics.phy-astr.gsu.edu/hbase/Sound/tralon.html
I am trying to understand why perpendicular motion is not possible in liquids or gases.

The above link doesn't explain why perpendicular motion is not possible in liquids or gases.

vcsharp2003 said:
I am trying to understand why perpendicular motion is not possible in liquids or gases.
You need to be careful here. This is true for waves in the bulk of an infinite fluid/gas lacking rigidity. At a surface, the surface tension allows a host of different types of waves, but the details are complicated. FYI

berkeman and vcsharp2003
vcsharp2003 said:
I am trying to understand why perpendicular motion is not possible in liquids or gases.
The case with liquids and gases is that liquids and gases don't have that much shear strength. Transverse waves need a medium rigid enough to propagate, which liquids and gases can't provide.

vcsharp2003
hutchphd said:
You need to be careful here. This is true for waves in the bulk of an infinite fluid/gas lacking rigidity.
So, it seems there is no restoring force like tension in a rope or surface tension on liquid surface, that can pull back a perpendicularly displaced part of the medium. The rope tension or the surface tension provide the restoring force as well as a force to displace perpendicularly the next part of the rope or liquid. That is why a transverse wave can exist on the surface of a pond but not deep underwater.

Is above explanation valid? Mechanical waves should follow the Newton's laws of motion. (Unlike electromagnetic or light waves).

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vcsharp2003 said:
So, is the presence of shear force in liquids and gases responsible for perpendicularly displaced sections of medium to not come back to original position?
Shear force seems to be a force parallel to the plane being cut/sheared. It seems to prevent elasticity by exerting a force pointing away from equilibrium position of the displaced part.
No, it's the near absence of shear force. If of two adjacent blocks of water one moves sideways there's not much force dragging the other with it.

vcsharp2003

## 1. What is a mechanical transverse wave in solids?

A mechanical transverse wave in solids is a type of wave that travels through a solid medium, causing particles of the medium to vibrate perpendicular to the direction of the wave's propagation. This type of wave is commonly observed in materials such as metal, wood, and rubber.

## 2. How does a mechanical transverse wave propagate through a solid?

A mechanical transverse wave propagates through a solid by transferring energy from one particle to the next. As the wave travels, each particle in the medium vibrates perpendicular to the direction of the wave's propagation, passing on its energy to the next particle.

## 3. What is the mechanism behind the propagation of a mechanical transverse wave in solids?

The propagation of a mechanical transverse wave in solids is due to the elastic properties of the medium. When a force is applied to one end of the solid, it causes a displacement of particles, which in turn creates a restoring force that propagates through the medium as a wave.

## 4. What factors affect the speed of a mechanical transverse wave in solids?

The speed of a mechanical transverse wave in solids is affected by the density and elasticity of the medium, as well as the frequency and wavelength of the wave. Generally, denser and more elastic materials will have a higher speed of propagation for transverse waves.

## 5. How is the amplitude of a mechanical transverse wave in solids related to its energy?

The amplitude of a mechanical transverse wave in solids is directly proportional to its energy. This means that a wave with a larger amplitude will have more energy than a wave with a smaller amplitude. This relationship is described by the equation E ∝ A2, where E is the energy and A is the amplitude of the wave.

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