pressure in liquid and gases

• What is a fluid?

  A substance that can flow
• What is the unit of pressure equal to one newton per square metre?

  Pascal (Pa)
• Why does the pressure in a liquid increase with depth?

  Due to the weight of the liquid above
• Why does the pressure in a liquid depend on the density of the liquid?

  Weight of a liquid depends on its density
• What is upthrust?

  The resultant force due to pressure difference
• What will an object placed in a fluid do if its weight is equal to the upthrust?

  It will float
• What will an object placed in a fluid do if its weight is greater than the upthrust?

  It will sink
• Why does an object that is more dense than a fluid sink if placed in the fluid?

  Weight is greater than the weight of fluid displaced
• Why does an object that is less dense than a fluid float if placed in the fluid?

  Weight is less than the weight of fluid displaced
• Does an object that is partially submerged in a fluid experience greater pressure on its bottom or top surface?

  Greater pressure on its bottom surface
• What is the Earth's atmosphere?

  The layer of air that surrounds the Earth
• What is atmospheric pressure caused by?

  Air molecules colliding with surfaces
• Why does atmospheric pressure decrease with increased altitude?

  Less weight of air above a surface
• How does the height of the atmosphere compare to the radius of the Earth?

  It is smaller than the radius of the Earth
• What is a fluid?

  A substance that can flow
• What are the two types of fluids?

  Liquids and gases
• Why does pressure in a liquid increase with depth?

  Due to the weight of the liquid above
• What does the weight of a liquid depend on?

  Its density
• How can pressure in a column of water be calculated?

  Using pressure = height × density × gravity
• What is the formula for pressure in a liquid column?

  p = hpg
• How do you calculate the difference in pressure at different depths?

  Subtract the smaller pressure from the larger
• What is the unit of pressure?

  Pascal (Pa)
• How is pressure defined?

  Force acting per square metre
• How can pressure be calculated?

  Pressure = force / area
• What happens if holes are made in a column of water?

  Water spurts out further from the bottom hole
• What is upthrust?

  Upwards force on a submerged object
• What causes upthrust on an object in a fluid?

  Difference in pressure between top and bottom
• What will happen if an object's weight equals the upthrust?

  The object will float
• What will happen if an object's weight is greater than the upthrust?

  The object will sink
• Why does a dense object sink in a fluid?

  Its weight is greater than the upthrust
• Why does a less dense object float in a fluid?

  Its weight is less than the upthrust
• Where does an object experience greater pressure when submerged?

  On its bottom surface
• What surrounds the Earth?

  The atmosphere
• What causes atmospheric pressure?

  Air molecules colliding with surfaces
• Why does atmospheric pressure decrease with altitude?

  Fewer air molecules above the surface
• How does the density of the atmosphere change with altitude?

  It decreases with increasing altitude
• How does the height of the atmosphere compare to the Earth's radius?

  It is smaller
• What are the factors that can increase pressure?

  • Increasing the force
  • Decreasing the area
• What is Pascal's principle?

  • Pressure applied to a fluid in a closed container is transmitted throughout the fluid.
  • Pressure is amplified at narrow necks of containers.
• What is the relationship between depth, density, and pressure in a liquid?

  • Pressure depends on depth and density.
  • As depth and density increase, pressure increases.