PRESSURE IN LIQUIDS AND
GASES
BY ANISA FARAH
YEAR 8 STALWARTS
PHYSICS
INTRODUCTION TO PRESSURE
• WHAT IS PRESSURE?
• PRESSURE IS A CONTINUOUS PHYSICAL FORCE EXERTED ON OR AGAINST AN
OBJECT BY SOMETHING IN CONTACT WITH IT.
• THE FORMULA OF PRESSURE IS FORCE/AREA (P=F/A)
PRESSURE IN LIQUIDS
• LIQUIDS EXERT PRESSURE EQUALLY IN ALL DIRECTIONS
• PRESSURE IN A LIQUID INCREASES WITH DEPTH
FACTORS AFFECTING PRESSURE IN LIQUIDS
• AREA: THE BIGGER THE AREA, THE SMALLER THE PRESSURE
• FORCE: THE GREATER THE FORCE, THE GREATER THE PRESSURE
• HEIGHT OR DEPTH: AN INCREASE IN HEIGHT OR DEPTH LEADS TO GREATER
PRESSURE
• DENSITY OF THE LIQUID: THE HIGHER THE LIQUID DENSITY, THE GREATER THE
PRESSURE
PRESSURE IN GASES
• GASES ALSO EXERT PRESSURE IN ALL DIRECTIONS.
• PRESSURE IN GASES ALSO INCREASES JUST LIKE IT DOES IN A LIQUID. THE ONLY
DIFFERENCE IS THAT THE PRESSURE INCREASE WITH DEPTH IS MUCH FASTER IN
A LIQUID, DUE TO ITS HIGHER DENSITY. LOOK AT IT THIS WAY: IF GAS PRESSURE
DIDN'T INCREASE WITH DEPTH, AIRLINERS WOULDN'T NEED PRESSURISED
CABINS.
FACTORS AFFECTING PRESSURE IN GASES
• TEMPERATURE: THE HIGHER THE TEMPERATURE, THE GREATER THE PRESSURE
• VOLUME: THE HIGHER THE VOLUME, THE HIGHER THE PRESSURE
• NUMBER OF PARTICLES: PRESSURE INCREASES WITH THE NUMBER OF PARTICLES
ATMOSPHERIC PRESSURE
• THE ATMOSPHERE EXERTS PRESSURE ON EVERYTHING ON EARTH. AIR PRESSURE
DECREASES WITH ALTITUDE (HIGHER UP = LOWER PRESSURE).UNITS: MEASURED
IN PASCALS OR MMHG (MILLIMETRES OF MERCURY).
EFFECTS OF ATMOSPHERIC PRESSURE
• THE BOILING POINT OF LIQUIDS CHANGES WITH ATMOSPHERIC PRESSURE (E.G.,
LOWER BOILING POINT AT HIGH ALTITUDES).
• HUMAN BODY ADAPTATION TO ATMOSPHERIC PRESSURE.
MEASURING PRESSURE
• INSTRUMENTS: BAROMETER FOR ATMOSPHERIC PRESSURE, MANOMETER FOR GAS
PRESSURE.
• EXAMPLES
• EXAMPLES: MERCURY BAROMETER AND ANEROID BAROMETER.
APPLICATIONS OF PRESSURE IN EVERYDAY
LIFE
• SCUBA DIVING: PRESSURE INCREASES AS DIVERS GO DEEPER.
• AIRPLANES: PRESSURIZED CABINS TO MAINTAIN COMFORTABLE CONDITIONS
FOR PASSENGERS.
CONCLUSION
• PRESSURE PLAYS AN IMPORTANT ROLE IN BOTH LIQUIDS AND GASES.
• UNDERSTANDING PRESSURE IS CRUCIAL IN EVERYDAY LIFE (E.G., WEATHER,
ENGINEERING, HEALTH).