U3f – L3

1. Take out your homework problem worksheet so that we can go over it now.

March 17, 2010

DRILL

U3f – L3

• Technology – the application of knowledge, tools, and skills to solve problems and extend human capabilities.

• Technology System – a group of subsystems working together to solve problems and extend human capabilities.

• Core Technologies – several engineering resources that are the “building blocks” of all technology systems.

• Volume – how much space an object occupies• Force – a push or pull• Pressure – a force applied over an area• Closed System – a system in which no fluid can enter or leave.• Open System – a system in which a fluid can enter or leave.• Fluid – a substance (as a liquid or a gas) that conforms to the

outline of its container• Fluid Technology – the technology of using fluid, either gas

(pneumatics) or liquid (hydraulic), to apply force or to transport.

Homework Review - #1

U3f – L3

• Air brakes on a truck• Tires on a car• Airfoils on an airplane• Warm-air heating ducts• Hydraulic jack• Plumbing in a school• Hydro-electric dam• Fuel pipelines • Streamlined surfaces of airplanes for efficient air flight• Rough surfaces of golf balls for efficient flight• Aerodynamic vehicle design for improved gas mileage

Examples of Fluid Technology:

Homework Review - #2

P = F / A(Pressure = Force / Area)

PV = k(Pressure x Volume = Constant)

P1V1 = P2V2

(Initial P x Initial V = Final P x Final V)

Homework Review - #3

U3f – L3

U3f – L3

A gas system has initial pressure and volume of 80 psi and 6 L. If the volume changes to 10 L, what will the resultant pressure be in psi?

Homework Review - #4

Step 1: Write given information

P1 = 80 psi

V1 = 6 L

P2 = ?

V2 = 10 L

Step 2: Write the formula and solve

P1V1 = P2V2

(80 psi) x (6 L) = P2 x (10 L)

480 psi*L = P2 x (10 L)

10 L 10 L

P2 = 48 psi

U3f – L3

A sample of hydrogen gas is compressed from 300 cm3 to 2.5 cm3. Its pressure is now 5 psi. What was the original pressure of the helium?

Homework Review - #5

Step 1: Write given information

P1 = ?

V1 = 300 cm3

P2 = 5 psi

V2 = 2.5 cm3

Step 2: Write the formula and solve

P1V1 = P2V2

P1 x (300 cm3) = 5 psi x (2.5 cm3)

P1 x (300 cm3) = 12.5 psi*cm3

300 cm3 300 cm3

P2 = 0.0417 psi

U3f – L3

• Open System - a system in which a fluid can enter or leave

- Irrigation systems, forced hot air, engines, etc.• Closed System - a system in which no fluid can enter or

leave.

- Radiator heating/cooling, hydroponics, etc.• Valve – a mechanical device that starts, stops, or regulates

the flow of a fluid.• Meter – an instrument for measuring the quantity of water

passing through a particular outlet.• Resistance to flow:

Fluid Systems

U3f – L3

Problem (copy this problem):1. The diagram below illustrates how hydraulic brakes in a

car work. The pedal must be pressed with a force of 10 lbs. The surface area of the piston connected to the pedal is .5 square inch. If the surface area of the piston connected to the other end of the brake line is 1 square inch, what is the force applied to that piston?

P1 = P2

Boyle’s Law

P1 = F1 / A1 P2 = F2 / A2

U3f – L3

Problems

Solution:Step 1: Write given information

P1 = ? P1 = ?

F1 = 10 lbs. F2 = ?

A1 = 0.5 in2 A2 = 1 in2

Step 2: Write the formula and solve for the unknowns

P1 = F1 / A1

P1 = (10 lbs) / (0.5 in2)

P1 = 20 psi

P1 = P2 = 20 psi

F2 = 20 psi x 1 in2 = 20 lbs.

P2 = F2 / A2 F2 = P2 x A2

U3f – L3

Problems

P1 = 20 psi

F1 = 10 lbs

A1 = 0.5 in2

P2 = 20 psi

F2 = 20 lbs

A2 = 1 in2

What is the mechanical advantage of this system?

MA = L / F MA = (20 lbs)/ (10 lbs) MA = 2

Complete the fluid technology problem sheet.

U3f – L3