P11 Force and Pressure

• What is pressure defined as?

  Force per square metre on a surface
• What is the unit of pressure?

  Pascal (Pa)
• How is pressure calculated?

  Pressure = force / area
• What is the formula for pressure?

  p = F / A
• What is a fluid?

  A substance that can flow
• What types of substances are classified as fluids?

  Liquids and gases
• What happens when fluid particles collide with a surface?

  They exert a force at right angles
• Why does pressure in a liquid increase with depth?

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

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

  Using height, density, and gravity
• What is the formula for pressure in a column of liquid?

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

  Subtract smaller pressure from larger pressure
• What happens if holes are made in a column of water?

  Water spurts out from the holes
• Why does water from a hole at the bottom spurt out further?

  It is under more pressure
• What is upthrust?

  Upwards resultant force on submerged objects
• What causes upthrust on a submerged object?

  Greater pressure on the bottom surface
• When will an object sink in a fluid?

  If its weight is greater than upthrust
• What determines whether an object floats or sinks?

  The object's density compared to fluid density
• When will an object float in a fluid?

  If its weight equals the upthrust
• What is the upthrust on an object equal to?

  The weight of the fluid it displaces
• What happens to an object denser than the fluid?

  It sinks because weight is greater
• What happens to an object less dense than the fluid?

  It floats because weight is less
• What surrounds the Earth?

  A layer of air called the atmosphere
• What causes atmospheric pressure?

  Air molecules colliding with surfaces
• How does atmospheric pressure change with altitude?

  It decreases as height increases
• Why does atmospheric pressure decrease with altitude?

  Fewer air molecules above the surface
• What happens to the density of the atmosphere with altitude?

  It decreases with increasing altitude
• What is the effect of fewer air molecules on atmospheric pressure?

  It causes pressure to decrease
• What are the key concepts of pressure in fluids?

  • Pressure is force per area (Pa)
  • Fluids can flow (liquids and gases)
  • Pressure increases with depth due to weight of liquid
  • Upthrust is the resultant force on submerged objects
  • Atmospheric pressure decreases with altitude
• How do you calculate pressure in a column of liquid?

  1. Use the formula: p = hρg
  2. Identify height (h), density (ρ), and gravitational field strength (g)
  3. Calculate pressure at different depths if needed
• What factors affect whether an object floats or sinks in a fluid?

  • Weight of the object
  • Upthrust experienced by the object
  • Density of the object compared to the fluid
• What is the definition of altitude?

  Height above a surface
• What is the definition of atmosphere?

  The layer of air surrounding Earth
• What is atmospheric pressure?

  Pressure caused by air molecules colliding
• What is the definition of density?

  Mass per unit volume
• What does it mean to displace?

  To push out of the way
• What is a fluid?

  A substance that can flow
• What is gravitational field strength?

  Force per unit mass due to gravity
• What is a pascal?

  Unit of pressure equal to one N/m²
• What is pressure?

  Force acting per square metre