The strike zone varies from batter to batter. The width of the strike zone is the width of home plate. The height is from the batter's chest (usually the letters) down to the batter's knees. The strike zone doesn't necessarily go by how tall the batter is, but by how the batter's stance is in the batter's box while waiting for the pitch.
under your waist
Assuming you mean in baseball: The number of pitches in the strike zone versus the number of pitches outside the strike zone.
A ball in base ball is a ball outside of the strike zone. The strike zone is from mid-chest to knees and over home plate. Any ball inside the strike zone is a strike.
Traditionally, the strike zone extends from the waist to the letters of the team.
Umpires do not decide or announce changes in the strike zone, that is determined by the MLB Rules Committee. The last such change by the committee was in 1996, when the lower limit of the strike zone was changed from the top of the knees to the bottom of the knees. Umpires simply call the strike zone on what THEY PERCEIVE as the size of the zone in the rules in effect at the time.
A strike out is when a batter has two strikes (times when they either swing and miss or don't swing at a pitch in the strike zone) and they either don't swing at another pitch in the strike zone, or swing, and miss (if they make contact, but hit the ball foul, it's not a strike out)
It would be a ball
No - only a piece of it - doesn't even need to be 50% or more - as long as the umpire sees ANY part of it in the zone its a strike
Because it shows the ump where his knees are for the strike zone
Mike Piazza's Strike Zone happened in 1998.
According to MLB Rule 2.0, the Strike Zone is defined as: "The Strike Zone is defined as that area over homeplate the upper limit of which is a horizontal line at the midpoint between the top of the shoulders and the top of the uniform pants, and the lower level is a line at the hollow beneath the kneecap. The Strike Zone shall be determined from the batter's stance as the batter is prepared to swing at a pitched ball."