Pistons and cylinders

Let's take a look!

What type of experiment is this?

Experimental procedure and explanation:

• This is an experiment wherein water flows out of a measuring cylinder.
• We allow the weight to increase the water pressure to make it flow out more vigorously.
• First, let’s discuss how to make the tools. We cut the top of the plastic cup with scissors to the same diameter as that of the inside of the measuring cylinder. Smaller sizes cause more water leakage, and larger sizes cause more friction. Thus, we try to obtain the right fit. This is used as a piston.
• We attach a weight to the bottom of this cup with cellotape (in this case, brass cylinders weighing approximately out 330 g and 660 g are used).
• We drill a small hole in the side of the measuring cylinder (this time with a pin vise). (It is not possible to use a glass measureing cylinder because we cannot make a hole in it.)
• We fill the measuring cylinder with water and insert the plastic cup with the weight attached, as described previously. It can be observed that the pressure of the water increases.
• The total weight of the weight (magnitude of gravity) is received by the circular area of the cylinder cross-section, and the internal water pressure increases according to the amount of (magnitude of gravity)/(area)=(pressure). The energy of the water is greater and the rate of runoff is faster.
• The heavier the weight, the stronger the momentum.
• [Tip for making it] If the plastic cup is too large, it will be too tight, which may decrease the pressure. It is important that the top of the cup be cut carefully at the same height to ensure that it accurately matches the diameter of the cylinder. Another method to attain a suitable weight placing numerous coins in a plastic cup.
• This experimental video was produced with the support of JSPS Grant-in-Aid for Scientific Research 18K03956.

[Keywords]	Pressure, outflow velocity
[Related items]	The Height of Water and Its Energy, Water Fountain 2 (Using Pressure)
[Reference]	Ryozo Ishiwata and Mitsumasa Nemoto, "The Wonder of Flow", Kodansha Blue Backs, P34-37, P98-101 Ryozo Ishiwata, "Illustrated Fluid Dynamics Trivia", Natsume Publishing, P14-15, P102-193

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