Cartesian diver

Many devices and devices for the demonstration of one or another of the physical phenomena and laws are named after the geographical places where they were developed or where they were used. Today we want to introduce one of these devices. This is a Cartesian diver - an instrument for studying the conditions of sailing bodies and demonstrating the law of Archimedes.

How can you make a Cartesian diver? For a basis it is necessary to take a cylindrical thin-walled test tube or a similar vessel. Then pour about a third of the water and place it in a jar of water. Next, fill our diver with water using a pipette to the level when it swims, projecting above the surface of the water in the pot at a height of 1-1,5 mm. Now the Cartesian diver is ready to dive. A swim diver will be in a high transparent vessel, for example, a beaker. And we must take into account that the vessel will need to be closed with a thin rubber film or cork on top.

And what about the Cartesian diver, filled with water, to transfer from the can to the beaker? It's not so easy the first time, but after a certain workout it will turn out. So, the diver-tube is taken out from the jar by covering it tightly with a finger from the top, then turning it over, lowering it into a beaker with water and removing the finger under water. All, the diver can swim - with a successful dive a test tube floats in water almost completely immersed in it.

To immerse the Cartesian diver, you need to close the beaker with a thin rubber, for example from master or medical gloves. And it is better to close the vessel with a rubber stopper with a glass tube on which to put on a rubber tube about 10 cm long. The free end of the rubber tube is also closed with a stopper.

Demonstrate the conditions for swimming bodies as follows. Pressing on the rubber cover or squeezing with the fingers of a rubber tube, we will observe the immersion or ascent of our diver. You can choose such conditions, when the Cartesian diver will be at the bottom of the vessel, above or in the middle.

How can we explain what is observed from the point of view of physics? By squeezing a rubber tube or pressing on a rubber partition, we increase the pressure inside the device and a little water enters the diver-tube (by the way, it can also be seen - it should only be somehow, for example, using a thread or gum, to indicate the initial position of water in a test tube). The weight of the tube becomes larger than the buoyancy force and the test tube dips. When releasing a rubber tube or septum, compressed air in a test tube-diver squeezes out excess water, the test tube becomes lighter and floats up.

The behavior of the Cartesian diver demonstrates very well the principles of submerging submarines. In the hull of the vessel there are cisterns in which boats are filled with seawater for diving. When it is necessary to float, then with compressed air this water is squeezed out of the boat.

Just want to say that here is described only the general scheme of such an interesting physical experiment-demonstration, as the Cartesian diver. Of course, someone will test the tube with different colors or draw a diver on it, for example, using nail polish. And someone will stick a figure from above. If there is no test tube, you can experiment with an eye dropper. Either way, there is no limitation to fantasy and your Cartesian diver can be original and unique. Like the way to an incredibly interesting world of science...