# Grade 9 Fluids and Pressure, 7

## 21 terms

### fluid

non-solid state of matter in which the atoms or molecules are free to move past each other in gas or liquid
takes shape of container

### pressure

amount of force exerted per unit area of a surface

### pascal (Pa)

SI unit for pressure

### atmospheric pressure

pressure caused by the weight of the atmosphere

### Pressure Formula

pressure = force/area

### Fluid Pressure

increases as depth increases

### Depth Increases

Water pressure increases faster than
atmospheric pressure does
Water is denser than air

### Fluids Flow

high pressure areas to low pressure areas

### buoyant force

upward force that keeps an object immersed in or floating on liquid

### Archimedes Principle

the buoyant force on an object in a fluid is an upward force equal to the weight of the volume of a fluid that the object displaces

### Helium

less dense than air

### Why does an ice cube float in water?

Ice cube is less dense than water

### Sinking

object that is more dense that surrounding fluid

### Float

object that is less dense than surrounding fluid

### Overall Density of Object

changed by changing the object's shape, mass or volume

### Bernoulli's Principle

the principle that states that the fluid pressure DECREASES as the speed of fluid INCREASES

### lift

upward force on an object that moves in a fluid
determined by wing size and thrust

### thrust

pushing or pulling force exerted by the engine of an aircraft or rocket

### drag

force parallel to the velocity of the flow,
it opposes the direction of an aircraft
determines the speed of the aircraft

### Pascal's Principle

change in pressure in an enclosed fluid is transmitted equally to all parts of fluid

### Wing Shape

airplanes to take advantage of Bernoulli's Principle to achieve flight