Unit D Lesson D8
Completion requirements
Lesson D8: Hydraulic Systems
Video Lesson
Watch this video to learn how hydraulic systems provide a huge mechanical advantage for doing work.
Lesson D8: Hydraulic Systems
Figure D.2.8.1 – The Jaws of Life is a hydraulic rescue tool.
Figure D.2.8.2 – A Jaws of Life machine helps rescue passengers trapped in a vehicle.
Figure D.2.8.3 – A hydraulic rescue tool applies force to a stuck car door.
Reading and Materials
for This Lesson
Science in Action 8
Reading: Pages 296–300
Materials:
No additional materials needed for this lesson.
Jaws of Life
Large amounts of force transferred during a vehicle collision can cause the vehicle’s metal body to warp and bend. As a result, the vehicle’s doors can become stuck and not open properly. This prevents injured passengers from leaving the vehicle.
In this situation, firefighters and police officers need to cut the vehicle body apart to rescue passengers. Metal in a car is too strong to rip apart by hand. First responders once used saws to cut apart cars. However, saws were not the ideal rescue tool because they cut slowly and create sparks.
The Jaws of Life is a hydraulic rescue machine that can safely cut apart a car. It is made from an engine connected to a hydraulic pump. The high pressure generated in the hydraulic fluid applies a large amount of force to the cutting jaws. A hydraulic rescue machine has a huge mechanical advantage compared to prying the car apart by hand.
Large amounts of force transferred during a vehicle collision can cause the vehicle’s metal body to warp and bend. As a result, the vehicle’s doors can become stuck and not open properly. This prevents injured passengers from leaving the vehicle.
In this situation, firefighters and police officers need to cut the vehicle body apart to rescue passengers. Metal in a car is too strong to rip apart by hand. First responders once used saws to cut apart cars. However, saws were not the ideal rescue tool because they cut slowly and create sparks.
The Jaws of Life is a hydraulic rescue machine that can safely cut apart a car. It is made from an engine connected to a hydraulic pump. The high pressure generated in the hydraulic fluid applies a large amount of force to the cutting jaws. A hydraulic rescue machine has a huge mechanical advantage compared to prying the car apart by hand.
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Jaws of Life
Watch this video to see a demonstration of a hydraulic rescue machine cutting apart a car.
Watch this video to see a demonstration of a hydraulic rescue machine cutting apart a car.
Try It!
Using Hydraulic Mechanical Advantage
You have learned that pressure in a hydraulic system is the same everywhere. That means in a two-piston hydraulic machine, the pressure at the small piston is equal to the pressure at the large piston. Since pressure stays equal, and pressure is
equal to force divided by area (P=F/A), we can state the following ratio is true:
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In this activity, you will use a simulation to explore how you can use this ratio of equal pressure to calculate output force of a hydraulic system.
Download:
Instructions:
DOWNLOAD this document. It provides a table for you to record your calculations.
It also provides space for you to do your math work, so it would be a good idea to print this document. It also provides space for you to answer the questions later in this activity.
Instructions:
- Click here to open the hydraulic lift simulator. Notice the reset button in the lower right corner; you can click that
anytime to bring the simulation back to starting conditions. Repeatedly click the “expand” and “collapse” arrows to see the size of piston 2 change (there are 4 sizes for piston 2).
- Piston 1 is the small piston, and supplies the input force of 1000 N. Notice that the area of the small piston is 78.54 square centimetres (cm2). Normally, area is recorded in square metres (m2) for pressure calculations, but
square centimetres (cm2) will work for this activity.
- Piston 2 is the large piston and produces the output force. Collapse piston 2 to the smallest size and you will notice that the mechanical advantage is 2.25. Check the area of the piston and make sure it matches what is in the observation table.
- Repeat step 3 for each size of piston 2.
- For the mechanical advantage of 2.25, calculate the Large Output Piston Force. Use the ratio to do this. The first calculation has been done for you and the result has been entered in the observation table.
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- Repeat step 5 for the other three mechanical advantages, and enter the results of your calculations in the observation table.
- Remember that machines that give you a mechanical advantage increase the amount of force you can apply. You can use this to double-check to see if your calculations are correct. For example, the first mechanical advantage is 2.25. Multiply that
by the Small Input Piston Force of 1000 N, and you get an answer of 2250 N for the Large Output Piston Force. This confirms that the ratio calculation based on pressure is correct. Use this mechanical advantage double-check to confirm all your
calculations.
- Now use the different piston 2 sizes and mechanical advantages to try to lift different loads. Note that the simulation has icons for a person (1000 N load), motorcycle (7000 N load), and car (20 000 N load). You can click on each icon to place
it on the second piston. Record what loads can be lifted in the last column of the observation table.
Observations:
Questions:
Think about the following questions very carefully. Then, type or write your answers. After you have your answers, click the questions for feedback.
Think about the following questions very carefully. Then, type or write your answers. After you have your answers, click the questions for feedback.
Using Hydraulic Mechanical Advantage - check your answers.
The output force increases as the output piston area increases.
The input and output piston pressures are the same for all four piston combinations. This confirms that pressure remains the same throughout a hydraulic system.
As the area of the output piston increases, the mechanical advantage of the system increases.
If the input and output pistons were the same size, they would have the same force. If the input and output forces are the same, the mechanical advantage equals 1. There is no force advantage for this hydraulic system.
If the input piston was larger than the output piston, the mechanical advantage would be less than 1. The system would not have a force advantage in lifting a heavy load, but the output piston would move faster than the input piston.
Figure D.2.8.4 – Hydraulic mining machines provide a large mechanical advantage to humans.
Figure D.2.8.5 – Mining by hand requires much more effort than using machines.
Massive Machines
Some of the biggest hydraulic vehicles in the world are found in Alberta. These vehicles are used to mine oil sands. Huge hydraulic shovels dig up oil sands and lift it into large hydraulic dump trucks. These dump trucks transport oil sands out of the mine pit to the extraction plant, where the oil and sand are separated. Massive machines provide a huge mechanical advantage for recovering oil sands quickly, with less human effort.
Some of the biggest hydraulic vehicles in the world are found in Alberta. These vehicles are used to mine oil sands. Huge hydraulic shovels dig up oil sands and lift it into large hydraulic dump trucks. These dump trucks transport oil sands out of the mine pit to the extraction plant, where the oil and sand are separated. Massive machines provide a huge mechanical advantage for recovering oil sands quickly, with less human effort.
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Huge Hydraulic Systems
An oil sands heavy machinery operator talks about her job in this video.
An oil sands heavy machinery operator talks about her job in this video.
This massive machine has teeth that cut through thick ice on airport runways. A hydraulic system lifts and lowers its teeth.
This massive boat lift uses hydraulics and pulleys to lift huge ships out of the water.
Connections
Figure D.2.8.6 – Automotive mechanics fix and maintain cars and trucks.
Figure D.2.8.7 – Aircraft mechanics make sure that airplanes are safe to fly.
Figure D.2.8.8 – Heavy duty mechanics often work on large industrial equipment.
>> Mechanics
Machines require maintenance so they continue to run properly. Machines sometimes break down and need to be repaired. Mechanics fix and maintain machines. Mechanics need to understand how all the parts in a machine work together.
There are many different kinds of mechanics. Automotive mechanics fix personal transportation vehicles, like cars and trucks. Airplane mechanics fix airplanes. Heavy duty mechanics work with large machinery, like construction and mining vehicles.
All of these types of mechanics need to understand how hydraulic and pneumatic systems operate. Cars and trucks have hydraulic brakes. Larger vehicles contain air brakes. Heavy duty machinery uses hydraulics to move levers. Airplane landing gear moves into position with a hydraulic system.
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Applied Mechanics
Heavy duty equipment mechanics repair and maintain large machinery, including hydraulic systems. Watch this video to learn more about this career.
Heavy duty equipment mechanics repair and maintain large machinery, including hydraulic systems. Watch this video to learn more about this career.
Watch this video to see how aircraft mechanics do detailed maintenance on airplanes.
A automotive mechanic fixes small vehicles, which include hydraulic systems.
Make sure you have understood everything in this lesson. Use the Self-Check below, and the Self-Check & Lesson Review Tips to guide your learning.
Unit D Lesson 8 Self-Check
Instructions
Complete the following 6 steps.
Don't skip steps – if you do them in order, you will confirm your
understanding of this lesson and create a study bank for the future.
- DOWNLOAD the self-check quiz by clicking here.
- ANSWER all the questions on the downloaded quiz in the spaces provided. Think carefully before typing your answers. Review this lesson if you need to. Save your quiz when you are done.
- COMPARE your answers with the suggested "Self-Check Quiz Answers" below. WAIT! You didn't skip step 2, did you? It's very important to carefully write out your own answers before checking the suggested answers.
-
REVISE your quiz answers if you need to. If you answered all the questions correctly, you can skip this step. Revise means to change, fix, and add extra notes if you need to. This quiz is NOT FOR MARKS, so it is perfectly OK to correct
any mistakes you made. This will make your self-check quiz an excellent study tool you can use later.
- SAVE your quiz to a folder on your computer, or to your Private Files. That way you will know where it is for later studying.
- CHECK with your teacher if you need to. If after completing all these steps you are still not sure about the questions or your answers, you should ask for more feedback from your teacher. To do this, post in the Course Questions Forum, or send your teacher an email. In either case, attach your completed quiz and ask; "Can you look at this quiz and give me some feedback please?" They will be happy to help you!
Be a Self-Check
Superhero!
Self-Check Quiz Answers
Click each of the suggested answers below, and carefully compare your answers to the suggested answers.
If you have not done the quiz yet – STOP – and go back to step 1 above. Do not look at the answers without first trying the questions.
Pressure equals force divided by area (P = F/A). The force applied to the input piston is 1200 N. The area of the input piston is 6 m2. 1200 N divided by 6 m2 equals 200 Pa of pressure.
The pressure of 200 Pa remains the same everywhere in the system. The area of the output piston is 18 m2. The force on the output piston divided by 18 m2 must equal 200. 3600 N divided by 18 m2 equals 200. The
force on the output piston is 3600 N.
Mechanical advantage equals the output force divided by the input force. The output force is 3600 N, and the input force is 1200 N. 3600/1200 equals a mechanical advantage of 3.
To achieve a greater force on the output piston, the input piston has to move a greater distance compared to the output piston.
Reducing the area of the output piston will increase the distance it moves. As long as the area of the output piston is greater than 6 m2 (which is the area of the input piston), the output piston will deliver a greater force than
the input piston.