Understanding Density, Pressure, and Fluid Systems

Know what the relationship is between density and temperature

Substances have different densities depending on their temperature.  

For example, a lake on a hot summer day. The surface temperature is warmer than the water beneath. The warm water floats on the cold because it has a lower density. 

Know why your ears pop when you are landing at an airport

Your ears pop from pressure change. The change of pressure outside causes your middle ear to have to readjust, resulting in a popping sound

Know the term buoyancy and why objects sink or float in a substance

Buoyancy is the ability of an object in a fluid to rise or sink due to density differences with its surroundings.

Know the densities of some common substances

Know Pascal's law and the differences between pneumatic and hydraulic systems

Pascal's law states that when force is applied to an enclosed fluid, the increase in pressure is transmitted equally to all parts of a fluid. Hydraulic systems are systems that use liquid and pneumatic systems use gas

Know why people use valves and provide examples of them as well

Hydraulic and pneumatic fluid systems consist of several components: 

• A pump: is when forces fluids through a system
• Conductors: provide a pay way to carry the fluid
• Valves: keep fluid moving in the desired direction at desired time
• A pressure gage: monitors pressure within the system

Ex: valves can be used to control the water level in the toilet tank

Ex: many veins in your body contain one-way valves

Ex: hose, controls the flow of water through the hose

What is a hydraulic Ram?

• Hydraulic rams allow this single worker to do the work of many people.

• The rams work by forcing fluid into either side of the piston, allowing powerful and precise movement in both directions.

• When fluid is pumped into the upper chamber, the piston is forced downward.

• Pumping fluid into the lower chamber forces the piston upward.

Combustion engine 

Internal combustion engine: a device that provides power by burning fuel within its cylinders

A car engine is called an internal combustion engine because it burns (combust) fuel in chambers in the engine the engine relies on valves to allow fuel to enter the chamber and exhaust gases to escape at the correct time and in the correct dire

Parts of the engine

(a) Air and fuel enter past the open intake valve. 

(b) Valves are closed to allow compression to the air-fuel mixture. 

(c) valves remain closed during combustion so no fuel or gases escape. The explosion pushes the pistons down. 

(d) exhaust valve opens to allow gases to escape.

Pro	Cons
Hydraulic rams allow this single worker to do the work of many people.	expensive
Efficient and precise	If the fluid leaks what are the damages?
Powerful used to move heavy loads	Not environmentally friendly with co2
	Affected by viscosity of fluids used within system