All fluids exert pressure like the air inside a tire. The particles of fluids are constantly moving in all directions at random. As the particles move, they keep bumping into each other and into anything else in their path. These collisions cause pressure, and the pressure is exerted equally in all directions. When particles are crowded together in one part of an enclosed space, such as the air particles first entering a tire, they quickly spread out to fill all the available space. That’s because particles of fluids always move from an area of higher pressure to an area of lower pressure. This explains why air entering a tire through a tiny opening quickly fills the entire tire.
Mary blew up the punching balloon for her daughter. She blew air into the narrow opening until the balloon was full then tucked it closed. After Ann played with it for awhile she gave it back to her mother. Mary opened the balloon back up and the air rushed out of the opening.
When Mary opened the ballon did the air spread out or stay together??