Friday is here again, and with it the weekly "A Taste of Physics" column — number 32.
This time — Pascal and Bernoulli join forces to cut through steel using… water!
-
In the video you can see a thin stream of water slicing through steel as if it were butter.
The cutting power is so intense that the padlock barely moves when the water jet splits it in two.
How does it work?
-
Water pressure is measured in a unit called PSI — Pounds per Square Inch.
The air pressure in your car's tires is around 32 PSI. In this cutting device, it reaches around 60,000 PSI!
This pressure is achieved in two stages.
In the first stage, a large standard piston applies pressure to the water inside a cylinder — say, 3,000 PSI.
The water then passes to a much smaller piston that acts as an amplifier, by way of Pascal's Law.
Pascal's Law states that pressure is applied equally in all directions and is proportional to area.
In this case, that means that because the smaller piston has a much smaller surface area, the pressure per square inch is significantly higher than that of the original piston.
From the small piston, the water is fired outward through a tiny orifice made of diamond.
According to Bernoulli's Law, water pressure decreases as its velocity increases.
This means that the release of pressure from the water bursting through the orifice translates into tremendous speed — 2.5 times the speed of sound.
-
Using water for cutting makes remarkably good sense.
Unlike diamond-coated saw blades, water requires no manufacturing, never wears out, never heats up, enables precise and delicate cuts, and is available in unlimited abundance.
The composition of the water stream varies depending on the material being cut and its thickness.
For delicate cuts, purified water is used; for tougher cuts, abrasive garnet powder is added to the water, increasing friction and cutting capability.
Shabbat Shalom 😊
#taste_of_physics