Physical Science chapter 13(testbook)

• When a two-liter plastic soda bottle completely filled with water, with its cap tightly screwed on, is sitting upright on a table, the pressure forces act equally in all directions against the inside of the bottle
• Pascal's principle


  The pressure exerted on a fluid in a closed container is transmitted equally throughout the fluid
• How a hydraulic system works

  1. Fluid in a closed container transmits pressure equally in all directions

  2. Pressure is applied at one point in the system

  3. This pressure is transmitted through the fluid

  4. The pressure causes a force to be exerted at another point in the system

  5. This force can be used to do work
• Lift


  The upward force exerted on an object immersed in a fluid, due to the pressure difference between the top and bottom of the object
• The speed of a fluid


  Inversely related to the pressure within the fluid
• Buoyancy


  The apparent loss of weight of an object submerged in a fluid
• Buoyant force


  The net upward force exerted on an object submerged in a fluid
• Archimedes' principle


  Determines if an object will float or sink in a fluid
• When an object is submerged in a fluid, the pressure forces acting on the bottom of the object are greater than those acting on the top</b>
• This pressure difference produces a net upward force called the buoyant force
• The buoyant force makes it easier to lift a submerged object and allows objects to float on the surface of fluids
• Buoyancy


  The ability of a fluid to exert an upward force on an object placed in it
• Buoyant force


  The apparent loss of weight of an object submerged in a fluid
• Archimedes' principle


  The buoyant force on an object is equal to the weight of the fluid displaced by the object
• Pressure increases with depth


  Forces pushing up on bottom of object are greater than forces pushing down on top
• Result is a net upward force - the buoyant force
• Density


  Ratio of an object's mass to its volume
• If object is less dense than fluid


  It will float
• If object is more dense than fluid

  It will sink
• Oil floats on water because oil is less dense than water
• Weight


  Force of gravity acting downward on object
• Buoyant force


  Equal to weight of volume of displaced fluid, acts upward on object
• When buoyant force equals weight

  Object floats or is suspended
• When buoyant force is less than weight

  Object sinks
• Suspended object has same density as fluid, buoyant force equals weight
• Ship sinks when weight becomes greater than buoyant force
• Denser fluids produce greater buoyant force for same displacement
• Ship's shape increases its volume and decreases its density, allowing it to float
• Helium and hot air balloons float because they are less dense than normal air
• Buoyant force equals weight of water displaced
• Small object floating at any level in water has same density as water
• 350-N block of wood floats, so buoyant force acting on it is 350 N
• Buoyant force


  The difference between the weight of each object in the air and its apparent weight in water
• 1.0 mL of water has a weight of 0.0098 N
• Data Table


  • Weight in Air (N)
  • Apparent Weight in Water (N)
  • Buoyant Force (weight in air - apparent weight in water, N)
  • Volume of Displaced Water (mL)
  • Weight of Displaced Water (N)
• Pressure = Force/Area
• Water pressure


  Increases as depth increases
• The pressure in a fluid at any given depth is constant and is exerted equally in all directions
• Air pressure


  Decreases as altitude increases
• Pascal's principle


  A change in pressure at any point in a fluid is transmitted equally and unchanged in all directions throughout the fluid