8.4 using pressure in liquids

• Science
• Middelbare school
• vwo
• Leerjaar 2

Lesson objectives 

8.4 Using pressure in liquids

• Explain how hydraulic machines work

• Name several examples of hydraulic machines

• Apply the formula for pressure to different situations involving hydraulic systems

  

When a force is applied to a contained, incompressible fluid, the pressure increases equally in all directions throughout the fluid

F2 bigger than F1                                  Output Force

P1=P2

input Force

F1=12 N, A1= 2 cm2

P1= F1/A1= 12/2=6 N/cm2

A2=2.10=20 cm2

P1=P2

F2= P.A

F2= 6 . 20=120 N

p

How hydraulic machines work

Hydraulic machines use liquids, which are incompressible. Force that is applied at one point is transmitted to another point using an incompressible fluid. The fluid is almost always an oil of some sort. The force is almost always multiplied in the process.

Hydraulic machines

Examples of hydraulic machines:

Hydraulic press

Hydraulic brake

Hydraulic jack

Hydralic lifts

Exercise

You push the plunger of syringe A with a force of 2 N. Syringe B has a plunger with an area that is 3 times the area of plunger A. What is the force produced by punger B?

to lift heavy objects

phet.colorado.edu

Exercise

Question: A hydraulic system is used to lift a 2000-kg vehicle in an auto garage. If the vehicle sits on a piston of area 0.5 square meter, and a force is applied to a piston of area 0.03 square meters, what is the minimum force that must be applied to lift the vehicle?

Answer: hydraulic lift solution

Exercise

Question: A barber raises his customer’s chair by applying a force of 150N to a hydraulic piston of area 0.01 m2. If the chair is attached to a piston of area 0.1 m2, how massive a customer can the chair raise? Assume the chair itself has a mass of 5 kg.