help with physics?

Question

why do a cylinder and a piston form a closed fluid system?

Answer 1

Literally, fluid (perhaps gas or some other liquid) is closed in the cylinder with a piston above.

This system is used in the hydraulic pump, where u have a cylinder/container/whatever and 2 pistons or different size, where one is very small. On one side, the user presses on the small pistion. It uses a small area, a certain force, to produce a relatively high pressure in the fluid, which then produces a large force with the pressure and large area of the next piston.

p = f/a

Answer 2

because there is no transfer in mass