Water Fountain 2 (Using Pressure)

Let's take a look!

Watch the video on YouTube.

What kind of experiment is this?

Experimental procedure and explanation:

• Drill a hole in the cap of a PET bottle and insert a straw through it.
• Fill the bottle with water. When squeezed firmly, the bottle becomes a water fountain. Squeezing the bottle increases the pressure of both the air and water in the PET bottle, causing water to spout through the straw. In principle, a water fountain is created by increasing the internal pressure in the bottle.
• The height (height A) of the spouting water shown in the figure corresponds to the increase in pressure in the PET bottle.
  (Upper Limit of Water Height) = (Increase in Water Pressure)/(Water Density)/(Gravitational Acceleration)
  The upper limit of the water height obtained using the above equation is the value when energy losses due to water viscosity and other factors are negligible. The actual height A of the spouting water is lower than the theoretical value due to energy losses.

  Ex)

  For example, the density of water is 1 g/cm3 (= 1000 kg/m3) and the gravitational acceleration is 9.8 m/s2. If the internal pressure is only 1500 Pa higher than atmospheric pressure, the upper limit for the water height is 1500/1000/9.8 = 0.153 m = 15.3 cm. However, because energy losses actually exist, the water height is lower than 15.3 cm.

• In the second experiment, another straw is inserted through the cap, and air is blown through that straw to increase the pressure of both the air and water in the PET bottle. With this method, a water fountain can be created in the same way.
• These two water fountains are created by water pressure.

[Keywords]	Pressure
[Related items]	Water Fountain 1、Water Fountain 3
[Reference]	“The Wonders of Flow,” Japan Society of Mechanical Engineering, Kodansha Blue Backs, pp.34-37 and 98-101 “Illustrated Fluid Dynamics Trivia,” by Ryozo Ishiwata, Natume Publishing, pp.14-15 and 192-193