Pressure and its effects

• Atmospheric Pressure


  • Atmospheric pressure acting on the suction cap holds it tightly on the wall. Can cause difficulties in breathing. An aircraft can fly at great heights where the air pressure is low. Air is pumped into the aircraft so that the air pressure inside is similar to that near the ground. Without this, passengers will have difficulty breathing
• Submarines

  • Submarines dive to great depths underwater. Their rigid metal bodies are built to withstand the very high pressure deep underwater
• Submarines

  • If the submarine dives beyond a certain depth, the pressure may become too high and damage the submarine
• How do we calculate pressure?

  Pressure can be calculated using the formula P = F/A where P is pressure, F is force, and A is contact area. The unit of pressure is newton per square metre (N/m²) or pascal (Pa) where 1 Pa = 1 N/m². The pascal is the SI unit of pressure
• Factors that affect liquid pressure: P-density in Kg/m³, g=gravity N/kg, h = height or depth in m
• The water pressure deep in the ocean is very high. Underwater vehicles must be very strong to withstand the water pressure
• Change in air pressure


  • Squashing a drink box (when we draw out the air inside the drink packet). By "sucking" through the straw, we lower the air pressure in the straw. The higher atmospheric pressure outside the straw pushes the liquid up the drinking straw. Holding a suction cup on the wall (pressing out the air within the cup)
• Pressure is defined as the force acting per unit area
• The air around us presses on us in all directions, known as atmospheric pressure. As we go higher, the air pressure decreases
• Water Supply

  • Water is delivered to and stored in tanks at the top of most high-rise buildings. This causes water in pipes below the tanks to be at a high pressure and ensures that water flows to the units below
• Liquids and gases exert pressure
• Articles must be very strong to withstand the water pressure
• 1 MPa = 1 x 10^6 Pa
• As we go higher, the air pressure decreases
• A pin can be easily pushed into wood but an eraser cannot, even if a large force is used
• The eraser has a larger area so the force is spread over a larger area (lower pressure)
• The studs on football boots provide a small surface area in contact with the ground. The boots sink easily into the ground because of the increased pressure, providing a better grip when the player is running
• Pressure can be increased by reducing area
• The air around us presses on us in all directions. This is known as atmospheric pressure
• Factors affecting liquid pressure

  • P-density in Kg/m^3
  • g=gravity N/kg
  • h = height or depth in m
• Low pressures are needed for moving on soft ground or snow without sinking
• Pressure


  The measure of the amount of force acting on a unit area
• Pressure can be reduced by increasing area
• The point of the pin has a small area so the force acts on a small area (greater pressure)
• When a larger surface is in contact with the ground, the pressure exerted on the ground is lower. This allows people, animals, and machines to move easily
• Pressure depends on force and area
• A sharp knife cuts more easily than a blunt knife as it has a small area in contact with an object. As the force acts on a small area, the pressure is high