What can you make this cute bubble hourglass?| Play

Today, when I think (JI) test (MO) (MO) birth (yu)

I saw the hourglass on the desktop

Suddenly watched

I plan to make a reverse hourglass to play

experiment equipment

Bid cup, plastic bottle, table tennis, syringes, scissors, diagonal clamps

experiment procedure

To knock on the blackboard, pay attention to safety, don't hurt yourself ~

Let's use a plastic bottle to make a long cylinder with a wide one -end and narrow cylindrical

It is best to use a smooth plastic bottle with smooth bottle curve

Cut off the tail of the plastic bottle

Use this cylinder to do some simple experiments first

For example, an experiment that junior high school just exposed to buoyancy:

Put the table tennis in the tube

Add water from the cylinder

We will find that table tennis will not float

But if we put the cylinder on the table

Or cover the mouth of the bottle with your hand

After a few seconds, table tennis will suddenly play up

Floating into the water instantly

Think of the essence of buoyancy

That is, the pressure difference between different fluid pressure on each surface of the object

The transformation between the two states in the experiment just now is very severe

But we can use some means to regulate this change

For example, inject water in table tennis:

Open a small mouth on the table tennis first

Use a syringe to pote the water in the table tennis

But don't note too full

As long as this mouth is not too big,

Not only the ball in the air will not flow out of the ball

The air in the ball is not soaked in the water, and the air in the ball will not be relieved

So now we put part of the ping -ping -pong ping -pong in the bottle

Tighten the bottle cap after pouring in water

Then calmly observe:

We can see that table tennis bounces up rhythmically and then falls down

The frequency of beating is getting higher and higher as the water surface below rises

And gradually float within a few seconds after the water was filled with water

The rhythm of ping -pong jumps here and the total length of the bouncing before floating

Related to the amount of water in table tennis

You can try the effect of different water injection on bouncing

The bouncing obtained when the water volume is appropriate is obvious and long -lasting

If the water injection is large

The entire device can also be used as an hourglass to use

When the table tennis is floating, it means that the hourglass time is here

Original understanding

When the bottle is open (as shown in the left side of the figure), below the table tennis is affected by the atmospheric pressure, and the part of the table tennis and water contact with the pressure of the atmospheric pressure and water pressure. Only the edge of the table tennis (on both sides of the red line in the figure) has a upper and lower surface on the upper and lower surfaces, which can provide a small amount of buoyancy. At the mouth.

When the bottle mouth is sealed with a bottle cap, desktop or hand (as shown in the right side of the figure), because some water will penetrate the space below due to the capillary on the surface of the table tennis, the air volume below will be reduced and the pressure will increase. When the pressure below increases to the ping -ups of the table tennis, table tennis will rise. Once the table tennis floats and the water quickly flows into the lower space, the table tennis is wrapped in water, and the complete buoyancy is great, so the speed of rebounding upward is extremely great.

However, if we pour ping -pong ball into part of the water, the overall quality of table tennis increases. When the table tennis bounces up, the acceleration is small, and the gap formed is very small. The air below the water will be the first in the form of bubbles. At this time, the upper and lower pressures of the interface of the table tennis and the bottle wall form a instantaneous balance. However, because the water tends to flow down the space at this moment , Block the air again. However, at this time, due to the reduction of the air volume, the penetration water that is needed will also become less in the next time, so the table tennis will bounce faster and faster. Until the air below was all refreshing, table tennis would rise.

If there is too much water in table tennis, when the overall density is close to the water, when the table tennis is "lifted" for the first time, the open channel is very narrow, which will form a delicate balance, so that the air below and the water above the water above the water will be on the top of the water above the water. The exchanges are alternated without continuing to make table tennis. The overall cycle is very stable, just like an hourglass.

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