8.2 Pressure Chapter 8 notes

General info Pressure - the amount of force acting over a given area on an object; an increase in pressure forces the particles closer together in a smaller volume Compression – a decrease in volume produced by a force Gasses are easily compressed due to the large amount of space between particles Air compressors are an example Pressure can cause explosion or implosions (inward collapse)  Solids and liquids are described as incompressible  Solids with air pockets can be compressed  Solids can appear to be compressed when they deform (deformation)

Pressure (p) = force (F) ÷ area (A) The units are N/m2 or a pascal (Pa) 1000 Pa is a kilopascal (kPa) More math! What do I know...write it down! What do I need to know...write it down! Choose the correct formula Put the number in and solve.

Practice problems 1. A vehicle loaded with garbage exerts 18 000 N of force on a scale that measures 6.0 m by 6.0 m. What pressure does the scale put on the spring below?

solution 1. A vehicle loaded with garbage exerts 18 000 N of force on a scale that measures 6.0 m by 6.0 m. What pressure does the scale put on the spring below? P = F ÷ A = 18 000N ÷ 36 m2 = 500 Pa

Another problem 2. A student sings on a stage while standing on a 2.0 m by 2.0 m platform. If the student weighs 800 N, what pressure does the platform put on the stage?

Second solution 2. A student sings on a stage while standing on a 2.0 m by 2.0 m platform. If the student weighs 800 N, what pressure does the platform put on the stage P = F ÷ A = 800 N ÷ 4 m2 = 200 Pa

Last problem 3. A large cement block is carried in the back of a pickup truck. The bottom of the cement block has dimensions of 8.5 m by 4.0 m and it weighs 23 800 N. What pressure does it put on the truck?

Final solution 3. A large cement block is carried in the back of a pickup truck. The bottom of the cement block has dimensions of 8.5 m by 4.0 m and it weighs 23 800 N. What pressure does it put on the truck? P = F ÷ A = 23 800 N ÷ 34 m2 = 700 Pa