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8.2 - Pressure. Pressure. Pressure – the amount of force acting over a given area on an object. Compression. Compression – a decrease in volume because of a force. Why do you think the volume decreases? Shouldn’t it stay the same??. Gases are Compressible ( con’t ).
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Pressure Pressure – the amount of force acting over a given area on an object.
Compression Compression – a decrease in volume because of a force. Why do you think the volume decreases? Shouldn’t it stay the same??
Gases are Compressible (con’t) Some uses for compressed gases:
Pressure and Kinetic Energy in Gases • Pressure can cause the particles energyto increase, which makes the particles move faster. • This can cause explosions!!
Pressure and Kinetic Energy in Gases (con’t) • Pressure can also cause implosions!!! • An implosion is a collapse inward.
Liquids and Solids are VERY Difficult to Compress • The volume does NOT change much in liquids and solids. Instead, the force is passed on to the particles directly. • This makes solids and liquidsincompressible.
Compression and Deformation • Solids can also appear compressed when they are deformed. Deformation – a change of shape without being forced into a smaller volume.
Comparing Pressure (con’t) UNITS: Force – N (Newton) Area - m² (square metres, or SQUAREA!!) Thus, Pressure is , or simply, Pa (Pascal) NOTE: 1 Pa is VERY small, so it is more common to see kPa (kiloPascal).
Calculating Pressure You can calculate the pressure an object exerts on a surface if you know its weight and the dimensions of the surface Example: • A BMX rider and bike weigh 1200 N. They are on a piece of sheet metal that is 1.0 m by 2.0 m. How much pressure does the sheet metal exert on the ground? P = P = P = P = P= 600 Pa
The Diving Bell • Why do you think the balloon shrinks??