* Pressure refers to a force pushing on a surface * Force and pressure are closely related, but are not the same thing * Pressure deals with force and the area that the force is applied to

* Pressure = force/area * Pressure is equal to the force exerted on a surface divided by the total area over which the force is exerted * The larger the surface area the lower the pressure * The smaller the surface area the higher the pressure

* Force is measured in Newtons * Area is measured in square meters (m²) * Pressure is measured in N/ m² * This unit is called a Pascal (Pa) * A more practical unit is the N/cm²

* Fluid- a substance that can easily flow * Liquids and gases * The molecules in a fluid move at all speeds and in all directions * They exert pressure on whatever they touch * All the forces exerted by the individual molecules in a fluid add together to make up the pressure exerted by a fluid

* Air pressure- air exerts pressure on you because it has mass * Air pressure is measured with a barometer * Air pressure decreases as elevation increases because there is less air above and therefore less pressure * Water pressure increases as depth increases because as you get deeper there is more weight to support.

* Buoyant force- force that water exerts on submerged objects – It is an upward force and acts against the pull of gravity – Makes objects in water feel lighter

* The buoyant force of an object is equal to the amount of fluid displaced by the object * An object in water loses some of its weight. The loss of weight is equal to the weight of the liquid displaced by the body.

* There is always a downward force on any object in water (this is the weight of the object) * If the weight is greater than the buoyant force the object will sink * If the weight is less than the buoyant force the object will float.

* The amount of matter per unit of volume * How much matter is in a specific space * Density depends on how tightly packed the molecules of the substance are. * An object that is more dense than the fluid in which it is immersed in sinks. * An object that is less dense than the fluid in which it is immersed in floats.

* Density depends upon an objects mass and volume * Density = mass / volume * Mass- the amount of matter in an object * Volume- how much space a three-dimensional object occupies * density is measured in g/cm³

* Water has a density of 1 g/cm³ * Anything that has a density greater than 1 will sink in water * Anything that has a density less than 1 will float in water * Any object that is more dense than the fluid it is immersed in will sink.

* Fluids always flow from areas of high pressure to areas of low pressure * You drink through a straw * Because there is less air in the straw, there is less pressure * The pressure in the cup remains the same * The fluid in the cup then flows into the straw because it is flowing from an area of high pressure to an area of lower pressure

* Air that is moving has lower pressure than air that is not moving. * Bernoulli’s Principle- states that as the speed of a fluid increases, the fluid’s pressure decreases. * Speed goes up, pressure goes down

* Bernoulli’s Principle is one of the reasons that planes can fly. * As the speed traveling over the wings increases, the pressure over the wings decreases * The high pressure under the wings then pushes the plane into the air * Planes also fly because of Newton’s 3 rd Law

* When force is applied to a confined fluid, an increases its pressure is transmitted equally to all parts. * Force pumps cause a fluid to move from one place to another by increasing the pressure in the fluid. * Forcing the air out creates low pressure, and allows the high pressure fluid to fill the reservoir * Eye dropper, heart, syringe, pipettes, many sea creature’s tentacles