Science Buddies: "Ask an Expert"

Imagine a tall vertical cylinder filled with air with a smoothly fitting piston suspended in its mouth.
(so that no air can escape past it)
The diameter of the cylinder / piston head is 2 inches. (or close in metric)
The length of the piston is unimportant and will be assumed as adequate for the question.
The height of the cylinder is assumed to be sufficient for the question.

QUESTION
How heavy does that piston have to be when dropped down the cylinder to compress the trapped air to a pressure
of 70 psi?

QUESTION 2
If we place a valve at the base of the cylinder and we want to vent the air at 70 psi
and
we want the piston to fall at a normal speed
and
we want to make the piston as light as possible
Q
What size should that vale be?

NB2
The core issue here is trying to understand the relationship between the piston weight and the valve;
and how to marry the lowest piston weight with the biggest valve.
Many Thanks to anyone who responds.

Hi adamwalker,

Is your question related to a K-12 science fair project? If so, what is the hypothesis you are trying to test? If not, then a different set of online forums will be able to help you. These forums are specifically for K-12 students, parents, and teachers working on science fair projects.

If I understand your question, the 'dropping' of the piston is not significant to the question. A cylinder with a diameter of 2" has an area of 3.1416 sq inches (A=π*r^2). Thus the weight of the piston to create a pressure of 70 psi would be 70*3.1416 or 219.9 pounds.

Unfortunately, I don't understand the second part of your question.

Rick Marz