Q1: Gauge pressure is

ANS:A - absolute pressure - atmospheric pressure

Absolute pressure refers to the total pressure exerted by a fluid, including atmospheric pressure. It's measured relative to a perfect vacuum, meaning it includes the pressure exerted by the atmosphere as well as any additional pressure from the fluid itself. Atmospheric pressure is the pressure exerted by the Earth's atmosphere at a given point. It's the force per unit area exerted against a surface by the weight of the air above that surface in the atmosphere of Earth (or that of another planet). The difference between absolute pressure and atmospheric pressure gives us the gauge pressure. Gauge pressure is the pressure measured above atmospheric pressure. It's the pressure measured by a pressure gauge. So, when we subtract atmospheric pressure from absolute pressure, we're essentially removing the contribution of the atmosphere, leaving us with the pressure exerted by the fluid (gas or liquid) alone. Mathematically, the formula for gauge pressure is: Gauge pressure=Absolute pressure−Atmospheric pressureGauge pressure=Absolute pressure−Atmospheric pressure This difference helps us understand the additional pressure beyond what the atmosphere exerts, which is crucial for many engineering and scientific applications.