# Sum of forces, vacuum and gravity

• Gh778
In summary: This will bring its center of mass back to the original position.In summary, the conversation discusses a theoretical study on the sum of forces in a system consisting of a vacuum object, a disk filled with liquid, and a black object attached to the disk. The force of buoyancy on the vacuum bubble is considered and it is questioned whether the liquid can compensate this force. It is also mentioned that the movement of a vacuum bubble in water will not change the center of gravity of the whole system.
Gh778
It's a theoretical study. I would like to understand how the sum of forces can be at 0 if I put an object (vacuum in it) in a big liquid disk (disk is fulled with liquid), the disk is big enough for agglomerate liquid (like this works with a planet, matter is agglomarate with gravity). There is no external circular wall for disk ! it's very important. I attach the vacuum object with something external at disk (black color). The vacuum object has an extenral force give by liquid, force of buoyancy, this force is transmited to black object. I study the sum of forces on all the system (vacuum object+disk+black object). What's compensate this force ? How liquid can compensate this force ? And if liquid compensate the force, this would say if I put a bubble in water the bubble go to one direction and water go to the contrary direction, this would change the center of gravity.

#### Attachments

• bp.jpg
12.5 KB · Views: 453
Last edited:
yes, the force of buoyancy

Gh778 said:
And if liquid compensate the force, this would say if I put a bubble in water the bubble go to one direction and water go to the contrary direction, this would change the center of gravity.
Center of gravity of the whole system will not move. Fluid will move one way, the vacuum box and whatever is attached to it will move the other way.

So, if you're right: imagine a fluid disk (or a sphere) without black solid. I put vacuum object in water, this don't change the CG. After, I let the bubble move, this move water in one direction and vacuum object in other direction, but the vacuum object has no weight, this move the CG ?

Last edited:
Even if your vacuum bubble has no mass, the fluid has. The vacuum bubble will move outwards, and the center of the fluid will be exactly at the position where the initial center of mass was. While the fluid moves around your bubble, the remaining fluid will move, too.

## 1. What is the sum of forces in a vacuum?

The sum of forces in a vacuum is zero. In a vacuum, there is no air resistance or other external forces acting on an object, so the net force is zero.

## 2. How does gravity affect objects in a vacuum?

Gravity still affects objects in a vacuum. The force of gravity is dependent on the masses of the objects and the distance between them, so even in a vacuum where there is no air or other forces, objects will still be pulled towards each other.

## 3. Can objects float in a vacuum?

In a vacuum, objects with a density less than the surrounding fluid (in this case, air) will float. This is because there is no buoyant force acting on the object in a vacuum, so if the object is less dense than air, it will float upwards.

## 4. How does the sum of forces change in a vacuum compared to Earth's atmosphere?

In Earth's atmosphere, there are additional forces acting on objects such as air resistance. In a vacuum, these forces are not present, so the sum of forces will be different. Additionally, the force of gravity will be the only force acting on objects in a vacuum, whereas in Earth's atmosphere, there may be multiple forces acting on the object.

## 5. Why is it important to understand the sum of forces in a vacuum?

Understanding the sum of forces in a vacuum is important for many scientific and technological applications. For example, in space exploration, understanding the forces acting on objects in a vacuum is crucial for designing and controlling spacecraft. It is also important in understanding the behavior of matter in extreme conditions, such as the vacuum of outer space.

• Classical Physics
Replies
16
Views
833
• Classical Physics
Replies
9
Views
1K
• Classical Physics
Replies
7
Views
758
• Classical Physics
Replies
13
Views
1K
• Classical Physics
Replies
5
Views
1K
• Classical Physics
Replies
12
Views
2K
• Other Physics Topics
Replies
4
Views
215
• Classical Physics
Replies
17
Views
985
• Mechanics
Replies
22
Views
1K
• Classical Physics
Replies
9
Views
1K