# Effect of water upthurst in vacuum conditions

• nilic1
In summary, the conversation discusses the effect of creating a vacuum above the water inside a bell jar on a floating sphere. The conclusion is that the sphere will still float, as both the pressure on the water and on the sphere are reduced.
nilic1

## Homework Statement

A sphere is enclosed in a bell jar half filled with water. The sphere floats. Air is pumped out to create a vacuum above the water inside the bell jar. Will the sphere float in the same way, float better or will it sink?

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## The Attempt at a Solution

My guess is that since there are no air particles pushing down on the water surface the sphere should sink more maybe not completely. Is this correct?

nilic1 said:
My guess is that since there are no air particles pushing down on the water surface the sphere should sink more maybe not completely. Is this correct?

There are also no air particles pushing down on the portion of the sphere that's above the water line. So has there been any net change to the equilibrium?

gneill said:
There are also no air particles pushing down on the portion of the sphere that's above the water line. So has there been any net change to the equilibrium?

I had omitted that fact! So the sphere would float just with or without vacuum above the water since both the pressure on the water and on the sphere are being reduced. Thank you so much.

## 1. How does water behave in a vacuum?

In a vacuum, water will rapidly evaporate and turn into water vapor due to the low pressure and lack of atmospheric molecules to hold it together. It will also freeze at a much lower temperature than at sea level due to the decreased pressure.

## 2. What is the effect of water upthrust in vacuum conditions?

In a vacuum, there is no upthrust or buoyant force acting on an object submerged in water. This is because there is no surrounding medium for the water to push against, so the object will sink to the bottom.

## 3. Can water be liquid in a vacuum?

Water can exist in a liquid state in a vacuum, but only at extremely low pressures and temperatures. This is due to the fact that water molecules will evaporate and turn into water vapor at a much faster rate in a vacuum.

## 4. How does the boiling point of water change in a vacuum?

In a vacuum, the boiling point of water decreases because the reduced pressure means that less energy is required for the water molecules to break free from the liquid and turn into vapor. This is why water will boil at lower temperatures at high altitudes.

## 5. What happens to the density of water in a vacuum?

The density of water will decrease in a vacuum because there is less pressure pushing down on the water molecules, causing them to spread out and take up more space. This is also why bubbles form when boiling water in a vacuum.

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