# How do forces propagate through the chain?

• B
• Fiziqs
In summary, the conversation discusses how gravitational force propagates through a chain and what would happen if the gravitational source or the hook suddenly disappeared. It explains that the gravitational force acts on the entire chain all the time, causing tension and a wave to propagate through the chain. However, the information about the disappearance of the gravitational source or hook would propagate at a slower speed, resulting in a delay between the top and bottom of the chain falling. It also mentions that the chain may experience some deformation and relaxation under gravity, causing the bottom to accelerate slightly.

#### Fiziqs

If I have a chain suspended from a hook, such that gravity is pulling it downward, how does that gravitational force propagate through the chain?

What would happen if the gravitational source suddenly disappeared?

What would happen if the hook suddenly disappeared?

What I'm interested in, is how the reaction propagates through the chain.

Fiziqs said:
how does that gravitational force propagate through the chain?
It doesn't. It acts on the entire chain all the time.

Fiziqs said:
What I'm interested in, is how the reaction propagates through the chain.

This might give you an idea:

A.T. said:
It doesn't. It acts on the entire chain all the time.
But even if the gravity acts upon the entire chain all the time, it's still a wave propagating through the chain, such that if the gravitational source should suddenly disappear, the bottom of the chain would be the first to be aware of the disappearance, correct? I would assume therefore that there would be no discernible change in the chain other than a loss of tension, as the wave propagated through it. Neither end of the chain should move because there's no force acting upon it. It's simply a matter of the gravitational wave propagating upward through the chain, and tension disappearing. Or would there be two waves propagating upward through the chain, one for gravity and one for tension?

On the other hand, if the hook should suddenly disappear, it's the information about the loss of the hook that has to propagate downward through the chain, this time only in the form of a loss of tension. But in this case the information should propagate at something significantly less than the speed of light. But I'm not sure when the information reaches the bottom of the chain, and when it begins to fall. There should be a delay between when the top of the chain begins to fall and when the bottom of the chain begins to fall. But is this only due to tension, or will the information reach the bottom of the chain before that?

Fiziqs said:
I would assume therefore that there would be no discernible change in the chain other than a loss of tension, as the wave propagated through it. Neither end of the chain should move because there's no force acting upon it.
Only if the chain is not stretched at all under gravity.. A real chain would have some deformation, and the relaxation would accelerate the bottom slightly.

Fiziqs said:
It's simply a matter of the gravitational wave propagating upward through the chain, and tension disappearing.
That isn't a gravitational wave

Fiziqs said:
Or would there be two waves propagating upward through the chain, one for gravity and one for tension?
No.

Fiziqs said:
On the other hand, if the hook should suddenly disappear,
That is basically what the slinky videos show in an exaggerated way (slinky is much more stretchable than a chain).

## 1. How do forces propagate through the chain?

Forces propagate through the chain through a series of interactions between individual particles. When a force is applied to one end of the chain, the particles in that end will push against the particles next to them, and this chain reaction will continue until the force reaches the other end of the chain.

## 2. What factors affect the propagation of forces through a chain?

The propagation of forces through a chain can be affected by several factors, including the type of material the chain is made of, the length and thickness of the chain, the angle at which the force is applied, and the presence of any obstacles or bends in the chain.

## 3. Can forces propagate through a chain without any loss of energy?

No, forces cannot propagate through a chain without any loss of energy. As the force travels through the chain, some energy will be dissipated due to friction between the particles and other external factors. This loss of energy may result in a decrease in the strength or intensity of the force by the time it reaches the end of the chain.

## 4. How does the speed of propagation of forces through a chain compare to the speed of light?

The speed of propagation of forces through a chain is much slower than the speed of light. While the speed of light is approximately 299,792,458 meters per second, the speed of forces propagating through a chain will depend on the material and other factors mentioned above, but it will generally be significantly slower than the speed of light.

## 5. Can a force be transmitted through a chain in both directions?

Yes, a force can be transmitted through a chain in both directions. When a force is applied to one end of the chain, it will travel through the chain in one direction, but if a force is applied to the other end, it will travel in the opposite direction. This is because the particles in the chain are able to move and interact with each other in both directions.