# Challenge question for physicists

• gunslingor
In summary, the question is whether a hypothetical balloon with virtually zero mass and infinite hardness would float in water. Despite the balloon's inability to bend or interact with the water, it would still float due to the upward buoyant force exerted by the difference in water pressure on the top and bottom surfaces. The hardness or contents of the balloon are not relevant in the calculation of buoyancy, as demonstrated by the example of a submarine.
gunslingor
Okay, I have been wondering this for a long time. The question concerns buoyancy of objects in water.

Question:
Imagine you have a balloon filled with air. Imagine the balloon has virtually zero mass, but actually has a virtually infinite hardness. You could replace the balloon with a force field or sorts, like star trek. So, will the hypothetical balloon float? The arrangement in itself would have less mass than water; so by this reasoning it will float. But it has infinite hardness and therefore cannot bend in the expected way (if you were to hold a real balloon by the filling point underwater, it would stretch out as you go deeper and deeper). So the water can have no direct or indirect interaction with the mass inside the balloon. So will the balloon float? If not, has as hardness been accounted for in buoyancy calculations?

I don't understand the issue. Why wouldn't it float? The calculation of buoyant force does not require any "bending" of the object.

Hardness, or interaction with the contents of the balloon are not relevant.

1. The pressure exerted on the top surface of the balloon is smaller than the pressure exerted on the bottom surface (because the top surface is at a smaller depth where the water pressure is smaller). This difference in pressures depends only on the density of water and the geometry of the balloon, and it gives rise to an upward buoyant force.

2. If this upward force exceeds the downward gravitational force on the balloon (determined by the mass of air in it), the balloon will float.

So the water does not need to interact with the insides of the balloon, only gravity does. And gravity doesn't care about the hardness of the balloon shell.

As a practical example, consider a submarine - essentially a steel balloon that is capable of floating.

Gokul43201 said:
Hardness, or interaction with the contents of the balloon are not relevant.

1. The pressure exerted on the top surface of the balloon is smaller than the pressure exerted on the bottom surface (because the top surface is at a smaller depth where the water pressure is smaller). This difference in pressures depends only on the density of water and the geometry of the balloon, and it gives rise to an upward buoyant force.

2. If this upward force exceeds the downward gravitational force on the balloon (determined by the mass of air in it), the balloon will float.

So the water does not need to interact with the insides of the balloon, only gravity does. And gravity doesn't care about the hardness of the balloon shell.

As a practical example, consider a submarine - essentially a steel balloon that is capable of floating.

Dah, I think I'm an idiot, lol. You explain it very well, which braught back a lot of examples from physics I had forgotten. For some reason, I think I had made the assumption that gravity couldn't interact with the balloon mass internal; I assumed that the waters interaction with gravity was the only effect.

## 1. What is a challenge question for physicists?

A challenge question for physicists is a complex and thought-provoking problem that requires scientific knowledge, critical thinking, and problem-solving skills to solve. It often involves applying principles and theories of physics to real-world scenarios or phenomena.

## 2. Why are challenge questions important in the field of physics?

Challenge questions are important because they allow physicists to test and expand their understanding of fundamental principles and theories. By solving challenging problems, physicists can also uncover new insights and push the boundaries of scientific knowledge.

## 3. How do physicists approach a challenge question?

Physicists approach a challenge question by first analyzing the problem and breaking it down into smaller, more manageable parts. They then use their knowledge of physics, mathematical equations, and experimentation to develop a solution or hypothesis. Collaboration with other physicists and utilizing advanced technology and equipment may also be involved.

## 4. Can non-physicists attempt to solve challenge questions?

Yes, anyone can attempt to solve a challenge question in physics. While a deep understanding of physics principles and theories may be necessary, critical thinking and problem-solving skills are also important in approaching and solving these complex problems.

## 5. What are the potential benefits of solving a challenge question in physics?

Solving a challenge question in physics can lead to a better understanding of fundamental principles and theories, as well as potential applications in real-world scenarios. It can also contribute to advancements in technology and scientific knowledge, and provide a sense of satisfaction and accomplishment for the physicist who solves it.

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