Pressure in Fluids

• A fluid can be either a liquid or a gas
• The pressure in fluids causes a force normal (at right angles) to any surface in contact with the fluid

  
• $Pressure =$$\frac{force\; normal\; to\; a\;surface}{area\;of\;that\;surface}$ $P =$$\frac{F}{A}$

  • Pressure (P) in pascals (Pa)
  • Force (F) in newtons (N)
  • Area (A) in metres squared (m$^2$ )
• $p=$$h\rho g$

  • Pressure (p) in pascals (Pa)
  • Height of the column (h) in metres (m)
  • Density of the liquid (ρ) in kilograms per metre cubed (kg/m$^3$)
  • Gravitational field strength (g) in newtons per kilogram (N/kg)
• A partially (or totally) submerged object experiences a greater pressure on the bottom surface than on the top surface which creates a resultant force upwards called the upthrust
• If upthrust is less than an objects weight then the object sinks
• If the upthrust is equal to an objects weight the object will float
• The size of upthrust acting on an object is the same as the weight of water displaced by the object
• An object more dense than water sinks
• An object the same density of water float is with the top inline with the water