Science 8 - Unit A - Mix and Flow of Matter Topic 7: Fluid Pressure

What is Pressure?  Pressure is the force acting perpendicularly on a certain area.  The formula for pressure is:  P = F/A where P=pressure, F=Force, A=area  Units for pressure are N/m2, but most people use the unit name pascal (Pa) for pressure. Note that 1 Pa = 1 N/m2  Pressure is the force acting perpendicularly on a certain area.  The formula for pressure is:  P = F/A where P=pressure, F=Force, A=area  Units for pressure are N/m2, but most people use the unit name pascal (Pa) for pressure. Note that 1 Pa = 1 N/m2

What about the pascal?  The pascal is such a small unit that most of the time when we talk about pressure we usually talk about it in kilopascals.  1 kPa = 1000 Pa.  The pascal is such a small unit that most of the time when we talk about pressure we usually talk about it in kilopascals.  1 kPa = 1000 Pa.

Compression  Compression - being squeezed into a small volume. Remember gases can be compressed, solids and liquids cannot. Also remember why according to the particle model of matter.  Compressibility - the ability to be squeezed into a smaller volume.  Incompressible - the inability to be squeezed into a smaller volume.  Compression - being squeezed into a small volume. Remember gases can be compressed, solids and liquids cannot. Also remember why according to the particle model of matter.  Compressibility - the ability to be squeezed into a smaller volume.  Incompressible - the inability to be squeezed into a smaller volume.

Applications of Compression  Because only gases can be compressed they are used to help absorb forces.  Airbags, foam bumpers, bubble-wrap, tires, etc. all use the compressibility of air to absorb shocks and protect the contents.  Because only gases can be compressed they are used to help absorb forces.  Airbags, foam bumpers, bubble-wrap, tires, etc. all use the compressibility of air to absorb shocks and protect the contents.

Air Pressure  Standard air pressure at sea level is 101 kPa.  Air pressure is measured by instruments called barometers.  Old fashioned barometers used mercury in a glass tube to tell air pressure. (See fig on p. 76)  Why don’t you feel this air pressure? Because you have the same air pressure inside your body as outside. However if you rapidly change altitude, you will feel the effects of air pressure changing.  Standard air pressure at sea level is 101 kPa.  Air pressure is measured by instruments called barometers.  Old fashioned barometers used mercury in a glass tube to tell air pressure. (See fig on p. 76)  Why don’t you feel this air pressure? Because you have the same air pressure inside your body as outside. However if you rapidly change altitude, you will feel the effects of air pressure changing.