Pressure in liquids and gases - OCR 21st CenturyPressure
Every living thing on Earth is in balance with the pressure of the air or water around it. Pressure helps blood to move around the body and allows organisms to breathe.
Pressure is forceA push or a pull. The unit of force is the newton (N). per unit area. Pressure determines the effect of a force on a surface.
Pressure exerted by different shoes
Different styles of shoe can cause different pressures due to their area.
Flat shoes spread the force over a large area, reducing the pressure. Snow shoes have a much larger area than feet to spread the force over a larger area and reduce the pressure on the snow - this stops people sinking into the snow.
High heeled shoes transfer the force through a much smaller area, causing a much greater pressure. It will hurt more if a person steps on someone鈥檚 foot in high heels than if they were wearing flat shoes. This is also why it hurts so much to accidentally step on a plug or stones barefoot - the force acts on a small area and the pressure is increased.
Calculating pressure in fluids
Liquids and gases are fluidA substance that can flow, such as a liquid or a gas.. The pressure in fluids causes a force normalActing at an angle of 90掳 to a surface or boundary. to a surface. A force that is normal to a surface acts at right angles (90掳) to it. To calculate the pressure at the surface of a fluid use the equation: