floating or sinking

• If holes are made in the side of a container filled with water, the water squirts out with the water from the bottom hole squirting out further than the water from the top hole
• Pressure of a column of liquid

  Pressure in Pascals = Height of column in meters x Density of liquid in kg/m^3 x Gravitational field strength in N/kg
• The equation for pressure of a column of liquid is provided in the exam, so you don't need to memorize it
• Calculating pressure at the bottom of a freshwater lake

  1. Height of column = 8 meters

  2. Density of fresh water = 1000 kg/m^3

  3. Gravitational field strength = 9.8 N/kg

  4. Pressure = 78,400 Pascals
• Factors affecting pressure of a liquid

  • Increases with depth (greater weight of liquid acting downwards)
  • Increases with density of liquid (greater weight acting downwards)
• Upthrust


  Resultant force acting upwards on an object immersed in a liquid, due to the difference in pressure between the top and bottom of the object
• For an object to float

  Upthrust must equal the object's weight
• The size of the upthrust acting on an object is the same as the weight of water displaced by the object
• Objects with different densities compared to water

  • Object less dense than water - floats high in water
  • Object same density as water - floats with surface at water surface
  • Object more dense than water - sinks