Larrys New truck

Larrys Truck ImprovementsLarry put a 6 lift kit on his Ford F-150 and a set of 33s Super Swamper Thornbird TiresThe Suspension System has been modified but the Brake System has not.Do You See Any Problems?GIT-R-DONE

What Parts Control the Stopping of the Truck?Master CylinderBrake Hoses/LinesWheel CylindersBrake Calipers

Larry has a Problem!What changes could you make to fix the problem?Bigger partsSuch as: Master Cylinder, Brake lines, Wheel Cylinders, and/or Brake Calipers

Pascals Law

Unlock the mechanics of the Hydraulic Braking System

Before we apply Pascals Law We must first review and be familiar withDiameter of a PistonRadius of the PistonArea of the top surface of the PistonMathematically speakingDiameter: The width of a circular or cylindrical object. Radius: The radius of a circle is half the diameter Area: Any particular extent of space or surface

Math Hands on Practice Measure across the top of the piston, through the center and record the diameter (inches)Calculate the radius of the pistonCalculate the area of the top of the piston A = r r or A = r2

Area Example

Diameter = 7 inchesRadius = 3 1/2 inchesArea = ?A= r2

3.14 (3 in)2 = 38.465 in2Area = 38.465 in2

HomeworkPractice skill workRead article: Effect of Oversize Tires on Braking Characteristics www.aamva.org/Documents/ vehStudyEffectOfOversizedTiresOnAlteredHeightVehicles.pdf -

Pascals LawIn the 1600's, the French scientist Blaise Pascal discovered a fact now known as Pascal's Law. It states that pressure at any point in a body of fluid is the same in every direction, exerting equal force on equal areas. This works for gases and liquids (both are fluids).

Pascals FormulaThis brings us to a very important formula:

P = Pressure, F = Force and A = Area This expresses that Pressure is Force per Unit Area. This is why pressure is usually expressed in pounds per square inch (psi).

Variations of Pascals LawPressure = Force divided by areaForce = Pressure times area

Area = Force divided by pressure

F

P AF =ForceP = PressureA = Area

Have you used formulas like Pascals Law? Where are they used?

Generic Inverse Variation Problem used in Algebra Time = Distance / RateOhms Law used in science class with electrical components

Using Pascals LawPascal's Law - gives us the mechanics to do a great deal of work with hydraulics. The drawing on the left shows that we can lift a large amount of weight with a small amount of effort. We can lift 100 pounds by applying just 10 pounds of force to the piston measuring 1 square inch

Basic automotive braking system

50 lbs force.5 sq in area of top of piston50 lbs divided by .5 = 100 psi

Where might Pascals Law be used?A twenty ton floor jack has a hydraulic piston with a 7 in diameter.60 pounds of force is being applied to the piston.Calculate the line pressure being exerted on the piston.

Solving a Pascals Law problemWhich version of Pascals Law will you use? Pressure = Force divided by area

Recall from earlier.. A= r2 3.14 (3 in)2 = 38.465 in2Area = 38.465 in2

P = (60pounds) / (38.465 in2)P = 1.56 pounds/ in2P = 1.56 psi

Using Pascals LawA caliper piston has a diameter = 1.5 inThe Master cylinder has 50 pounds per square inch (psi) line pressure applied to it.Determine the force exerted on the caliper piston.

Solving a Pascals Law problemWhich version of Pascals Law will you use? Force = Pressure times area

Recall how to find area.. A= r2 3.14 (3/4 in)2 = 1.77 in2Area = 1.77 in2 F = (50pounds/ in2) (1.77 in2)F = 88.5 pounds

Did Larry have brake failure?

Remember Larrys Truck ..The truck has a major braking problem.You suggested earlier that we replace it with bigger brake partsWhat do we need to know about the original braking system?

GIT-R-DONE

Facts about Larrys Truck in brake lines in bore master cylinder7/8 in bore wheel cylinders2 in caliper pistons

Can you fix Larrys truck?Devise a plan to fix Larrys truck based on Pascals Law and your knowledge of automotive systems that will remedy Larrys braking problems.Be sure to show all calculations and justify your solution plan in a written paragraph.

Remember Larry doubled the size of the original tire size..

Be thorough..Larry is depending on you

How would youGit-R-Done? GIT-R-DONE

Lessons 2 & 3: Pascal's Law