9.2 Pressure, Hydraulics, and Pneumatics Mechanics: Automotive Technology : 2 years at Holland College

For further reading on Archimedes

Working on report cards...sort of...

If you think you may have missed passing in some

assignments, come see me at break or lunch and I

can tell you what you are missing...

#helper#needycat#Bert

a) read 9.2 pages 348 to 359, take a look especially at the math section we will be doing.

b) key terms: (on looseleaf to pass in); p 348

compressibilityhydraulicshydraulic multiplicationhydraulic systemsincompressiblepascalpneumatic systemspressurestatic pressure

Checking concepts: (review of 9.1)

p. 347 Q 1, 2, 4, 6, 10. ON LOOSELEAF.

Pressure:

is the force acting on a certain area of a surface.

Ex: popping a balloon with finger or a needle, which works?

Force, Area and Pressure

Two Considerations:

1.) The larger the force, the greater the pressure.

2.) The smaller the area, the greater the pressure.

If someone stepped on your foot wearing either of these shoe...which would hurt more?

Ballerina: which scenario is the most likely to cause injury to her feet?

1) pass in note-taking handout 9.1 – 9.2 to white bin at front….I will still take them until Wed.

2) Thinking about pressure, force and surface area:

video "bed of nails" (2 min)

video "walking on eggs" (5min)

Calculating Pressure:

Pressure is calculated by measuring the force that is being exerted on an object and dividing it by the area over which the force is being exerted.

Units: pascals (Pa)

Pressure = Area (m2)

Force (N)

Newtons

m2= Pascals (Pa)

Sample Problem:

A serving jug hold 500 N of Kool-Aid. If the base of the serving jug is 0.05 m2, what pressure does the Kool-Aide exert on the base of the serving jug?

P = F / AP = 500 N / 0.05 m2P = 10 000 Pa

Calculating Force:

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

F = P x A

Units = N (Newtons)

Sample Problem:

If 63 000 Pa of pressure is being exerted on a rubber ducky with a area of 0.09 m2, how much force is being exerted on the rubber ducky?

F = P x AF = 63 000 Pa x 0.09 m2 F = 5670 N

Calculating Area:

Area (A) = Force (N)

Pressure (Pa)

Units = m2

Sample Problem:

If 500 N of force is being exerted on a ball creating pressure of 1600 Pa, what is the area of contact with the ball?

A = F / PA = 500 N / 1600 PaA = 0.3125 m2

Pressure =

Area (m2)

Force (N) Newtons

m2= Pascals (Pa)

Force = Pressure (P) x Area (A) = N (Newtons)

=

Area = Force (F)

Pressure (P) = m2

WORKSHEET: https://docs.google.com/document/d/1aByUzwCPdpj6Y9exr8EkPaLBx_aSHdxuf0Oc-jOvocU/edit?usp=sharing

NOTE: I will always give you the formulas but it is a good idea to memorize them...which many of you do because you are careful to show all of your work, which includes writing down the formula each time!