When you squeeze one end of a tube of toothpaste out the other end, you are watching
Pascal's principle in action. The principle was first stated clearly in 1652 by Blaise
Pascal (for who the unit of pressure is named):
A change in the pressure applied to an enclosed incompressible fluid is transmitted
undiminished to every portion of the fluid to the walls of its container.
Pascal's principle put more simply, basically means that an incompressible fluid
transmits pressure. This is the basis to hydraulic lever. In a hydraulic lever, for
example, you apply a force to the left-hand piston over a given area, this force is then
transformed in to a pressure which is transmitted through the hydraulic fluid or oil.
This pressure then transforms back in to an output force over another given area for the
Answered by: Dan Summons, Physics Undergrad Student, UOS, Souhampton
'One thing I have learned in a long life: that all our science, measured against reality, is primitive and childlike - and yet it is the most precious thing we have.'