J TUBE EXPERIMENTS

J TUBES

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TUBE #1

Setup

• A 30” long 1”inside diameter clear plastic hose [A] is bent into the shape of the letter “J”

• A ½” long ¼” inside diameter clear plastic hose [B] is inserted into the lower end of he J of the tube [A] and tightly clamped. The [B] tube opening is therefore named orifice [B1]

• A vessel [C] with approximately ½” diameter orifice [C1] in its bottom is being continuously refilled with water from an outside source so, that the water column above the orifice is no more than 1” high as the water keeps pouring out of the orifice [C1]. The water column height in [C] is regulated by overflow from the vessel [C]. A piece of coarse foam [C2] is placed and retained by a dab of glue above the orifice as a vortex breaker and outflow stabilizer.

• The vessel [C] is retained on a rather solid stand [D]

• The clear plastic tube [AB] is retained on the stand [D] so, that the orifice [B1] at the lover end of the tube [A] is about 14” below the orifice [C1] and aligned vertically with the orifice [C1]. The upper end of the tube [AB] is retained some 5” above the water level in the vessel [C]. The 14" of the height of the free falling stream needs to be tuned so, that the diameter of the water stream at its lower end closely matches the inside diameter of the tube [B] insert as it gets squeezed by the clamp.

Procedure

Outside water (tap) is allowed to flow into the vessel [C] with the orifice [C1] plugged with experimenter’s forefinger till the water column in the vessel reaches 1” height at overflow. Then the experimenter unplugs the orifice [C1] and the water streaming down (stream) is allowed to pour into the orifice [B1] of the initially empty tube combination [AB].

Result

The water column in the hose [AB] (column) rises with some air bubbles and a bit of splashing at the orifice [B1] till it reaches the level of the orifice [C1]. Further rise of the water column in the tube [AB] stops and stabilizes at this height, that is height of the orifice [C1]. Now all the water pouring from the orifice [C1] (stream) rebounds from the orifice [B1] and splashes under an angle of roughly 45 degrees up to a height, which varies between 1/2 and 2/3 of the height of the water stream falling from the orifice [C1]. This depends on how well the end of the tube [B], the orifice [B1] had been cut.

Conclusion

The water, which rebounds from the opening at the orifice [B1] retains most of its kinetic energy of its free fall as it hits the orifice [B1] and rebounds due to this energy. While some of the kinetic energy of the falling stream is spent on supporting of the water column in the tube [AB], most of the energy is retained by the rebound water and spent on its elevation to 1/2-2/3 of the falling stream. There is enough energy in the falling stream to press the water column in the tube [AB] higher, but this energy is not used up for this due to the unsuitable arrangement of the experiment. The stream is opposed head on by the water column in the tube [AB] , which can be remedied by improved setups.

The water in the down stream does not weight anything as a free falling column, but the water molecules in it weight their specific weight plus their kinetic energy while rebounding. Each molecule of falling water in the process of rebound at orifice [B1] is capable to support more than the weight of one molecule of water in the column in the tube [AB] and still retain more than half of its kinetic energy for its rebound and splash up and sideways, i.e. its speed and momentum. The water column in [AB] is supported mostly by centrifugal force of the half donut of rebounding water.

TUBE #2

Setup

Similar arrangement is set up with only one change. The original tube combination [AB] is replaced with single ¼” inside diameter clear plastic tube [BL] 30” long.

Procedure

Is identical to the procedure in “Tube #1” experiment.

Result

The water stream entered the tube [BL] and with virtually no bubbles began to rise up as water column up the tube [BL]. It has initially over flown the upper end of the tube [BL] about 4" above the water level in the vessel [C]. Never the less, the water stream begun to splash at the lower end of the tube [BL] and the water column begun to fall back to the height of the orifice [C1] where it settled. Then the water stream from the orifice [C1] splashed again to 1/2-2/3 height of water stream.

Conclusion

We can conclude the same as in Tube #1.

Note

A setup, which may coerce the kinetic energy of the water stream from the orifice [C1] to retain all its kinetic energy in one general direction and therefore support overflow at the upper opening of the J arrangement is described (rather crudely) in Ideas/U pump.