Science Focus Topic 9 Notes: Fluid Systems | Print |
Key Concepts:
  • Fluid systems are present in living things and human-made devices
  • Interpret the function of fluid systems within living things and human-made devices
  • Construct a diagram to illustrate components in a fluid system
  • Construct a functional fluid system using materials provided.
  • In a hydraulic lift, a small force applied to a small-area piston is transformed to a large force at a large-area piston. If a car sits on top of the large piston, it can be lifted by applying a relatively small force, the ratio of the forces being equal to the ratio of the areas of the pistons.

Even though the force can be much less, the work done is the same. Work is force times the distance, so if the force on the large piston is 10 times larger than the force on the smaller piston, the distance it travels is 10 times smaller.

Hydraulic Systems

Mechanisms that work because of the movement of a liquid, or the force exerted by a liquid within a closed system is called a hydraulic system.

Hydraulics can be applied to engineering devices involving liquids, usually water or oil.

Hydraulics deals with such problems as:

  • the flow of fluids through pipes or open channels
  • the design of storage dams, pumps, and water turbines
  • nozzles, valves, and jets, that control the flow of liquids
  • hydraulic actuators
  • hydraulic presses

The Hydraulic Press

(Activity 2-16) uses the principle of fluid pressure - a force applied to a confined liquid will be transmitted throughout the liquid.

Because force equals pressure multiplied by area, forces can be increase (by enclosing a liquid between two movable pistons of different areas)

Mechanical advantage
Is used in such hydraulic actuators as automobile brakes and the control flaps of airplanes. Hydraulic presses, invented by British engineer Joseph Bramah in 1796, are used to shape, extrude, or stamp metals and to test materials under high pressures.

Effort Force Advantage
The force is equal to the pressure multiplied by the area, so where the surface area is small, the force exerted is small, where the surface larger, the force exerted is larger.

Valves & Pumps

? interpret the operation of various kinds of valves
? interpret the operation of valves in the human heart
? interpret and explain the operation of pumps

Visit: Glossary of Pumps ... it's fantastic as a resource for this Topic.


  • Identify and interpret technologies that are based on buoyant force(e.g. design of ships and submersibles
  • Design of lighter-than-air craft
  • Measurement technologies based on use of hydrometers
  • Predict the effect of design on drag around an object traveling through a fluid (aerodynamics)
  • Design a streamlined device (hydrodynamics)

Practical Applications
Hydraulic car lift (p. 106)

Hydraulic Jacks

Fork-lift Trucks


Lifting Mechanism and Compression Mechanism on Garbage Trucks

Retractable wheels on airplanes p. 107

Water supply systems

Human body:
Circulatory System also: (Endocrine System) (Digestive system) (Respiratory System) p. 109

Water and compressed air are used to change the density of a submarine
(Check out the Submarine notes)

Hoses, toy water pistols. syringes.