How is toothpaste dispenced from tube (scientifically)?

Answer 1

Toothpaste is more or less incompressible. That means that, even though you can change the shape of a mass of toothpaste, you cannot easily compress it into a smaller volume.

When you apply pressure on an incompressible substance, the force is transmitted, molecule by molecule, throughout the substance. So when you push on one end, the force will get transmitted to other parts of the mass so that the other parts move as well. They will move in such a way as to preserve the mass's total volume.

If you have a big mass of toothpaste just sitting on the counter (not inside its tube), and you stick your finger into it, the parts immediately around your finger respond to the pressure and move out of the way. This preserves the volume and relieves the pressure, so the parts farther away from your finger don't feel the pressure and therefore don't move.

But when the toothpaste is confined within its tube, and you squeeze the tube's bottom end, the mass near your finger cannot "spread out" like it did in the first example. The mass near your finger presses against the side of the tube, but the side of the tube then presses back (this is Newton's 3rd Law). Thus the pressure in this area is NOT relieved, and is transmitted throughout the different areas of the mass. When the pressure reaches the mouth of the tube, it forces the mass through the opening.

Answer 2

I guess I would say that when the tube is squeezed, the volume of the tube is decreased, creating pressure inside the tube equally on all surfaces (Pascal) so the toothpaste moves out of the tube through the opening to an area of lower pressure outside the tube.

Answer 3

nick wow this question is so easy
the toothpaste tube is so compact that if you put a little pressure on any point of the tube then the toothpaste will come out.