.....but air is let out of it.......... it is factored into the equation, the 152 has the bleed hole on the rear of the pitot head
Nutloose, sorry but you are wrong. As Troy McClure said, the pitot measures static plus dynamic pressure. If there was a bleed hole, it wouldn't work.
It's so long ago since I flew a 152, that I cannot remember what the pitot/pressure head looks like, but I suspect the hole you are referring to is the static port.
I42