pressures

• Pressure


  Force per Unit Area
• Pressure in a fluid

  1. Particles able to move around

  2. Particles collide with surfaces and other particles

  3. Particles exert a force on the object they collide with

  4. Pressure is exerted on any surface in contact with the fluid
• Pressure in a fluid

  Force normal to a surface / Area of that surface
• Pressure in a Liquid Depends on Depth and Density
• Density


  Measure of the 'compactness' of a substance, i.e. how close together the particles in a substance are
• Calculating pressure in a liquid


  1. Height of the column of liquid (the depth)

  2. Pressure (Pa) = ρgh
• Standard form


  A is always a number between 1 and 10, Ax 10^n, n is the number of places the decimal point would move if you wrote the number out fully
• Upthrust and Atmospheric Pressure
• Upthrust


  • Force exerted upwards on a submerged object, equal to the weight of the fluid displaced by the object
• Object floats


  If its weight = Upthrust
• Object sinks


  If its weight > Upthrust
• Submarines use upthrust to sink and rise
• Atmospheric pressure


  Pressure created on a surface by air molecules colliding with the surface
• As altitude increases


  Atmospheric pressure decreases