pressure in a fluid

• What is pressure?

  
  

  What are fluids?

  Force per unit area

  
  

  Substances that can 'flow
• What does the pressure in fluids cause?

  - the pressure in fluids causes a force to act at right angles to it's surface.
• How can we calculate the pressure exerted by fluids?

  pressure (Pa) = force normal to a surface (N) / area of that surface (m²)

  
  

  p = F/A
• What does pressure in a liquid depend on?

  Depth and density
• What is density?

  Measure of how compact a substance is - how close particles are

  
  

  Density of gases can vary

  
  

  Density of liquids do not vary
• When we make a hole near the bottom a container filled with water, why does the water squirt out further than if we made a hole near the top of the container?


  - water at the bottom of the container is at a higher pressure
• What is the equation to calculate the pressure of a column of liquid?


  pressure (Pa) = height of the column (m) x density of the liquid (kg/m³) x gravitational field strength (N/kg)

  
  

  P = h x p x g
• Why does pressure increase with depth and density?

  Greater density = more particles available to collide so pressure is higher

  
  

  Greater depth = more weight of particles so increase in liquid pressure
• What is upthrust?

  The upwards force exerted by a fluid on a submerged object
• How do objects submerged in liquids experience upthrust?

  Pressure of fluid exerts force in every direction

  
  

  Pressure increases with depth

  
  

  Force exerted on the bottom is larger than the force acting on the top

  
  

  Causes the resultant force - upthrust
• What has to be equal for an object to be balanced and be able to float?

  Upthrust is equal to an objects weight
• Why does an object sink?

  If weight is more than the objects upthrust
• What is dependent on an objects ability to float?


  It's density
• What will happen to an object that is less dense than the fluid it is in?

  Displaces the volume of fluid that is equal to its weight before it is completely submerged

  
  

  Objects weight = upthrust

  
  

  Object floats
• What happens to an object that is denser than the fluid it is in?

  Unable to displace enough fluid to equal its weight

  
  

  Weight is larger than upthrust so it sinks