Pressure

• Units for pressure


  Pascals (Pa)
• How does a gas inside a container exert pressure on the container?

  The particles of gas move randomly and collide with the walls of the container. This force exerts a pressure on the container wall
• Pressure?


  A measure of the force per unit of area
• 3 factors that determine the pressure exerted by liquid?

  The depth. Greater depth=More pressure

  Density of liquid. More dense liquids exert greater pressure

  Gravitational field strength (9.8 N/m)
• Upthrust?


  Force that pushes upwards on an object submerged in a fluid(liquids and gases)
• What determines if the object in liquid sinks

  If the weight of the object is greater that the upthrust from the water it’ll sink
• What determines whether an object in liquid will float

  If the upthrust from the water is greater than the weight of the object, it will float
• Atmosphere?


  Layer of gas that surrounds the Earth
• Altitude 


  Height above the ground
• Atmospheric pressure 


  Total force of all the air particles constantly colliding with everything from all sides
• Atmospheric pressure decreases with altitude
• Why does atmospheric pressure decrease with altitude?

  Pulling force from gravitational field of earth becomes weaker as altitude increases so gas particles spread further apart and the atmosphere becomes less dense