Hydraulic/Pneumatic System

Transcription

1 Includes Teacher's Notes and Typical Experiment Results Instruction Manual and Experiment Guide for the PASCO scientific Model SE A Hydraulic/Pneumatic System 2000 PASCO scientific

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3 Copyright, Warranty, and Equipment Return Please Feel free to duplicate this manual subject to the copyright restrictions below. Copyright Notice The PASCO scientific A Hydraulic/ Pneumatic System Manual is copyrighted and all rights reserved. However, permission is granted to non-profit educational institutions for reproduction of any part of the manual providing the reproductions are used only for their laboratories and are not sold for profit. Reproduction under any other circumstances, without the written consent of PASCO scientific, is prohibited. Limited Warranty PASCO scientific warrants the product to be free from defects in materials and workmanship for a period of one year from the date of shipment to the customer. PASCO will repair or replace at its option any part of the product which is deemed to be defective in material or workmanship. The warranty does not cover damage to the product caused by abuse or improper use. Determination of whether a product failure is the result of a manufacturing defect or improper use by the customer shall be made solely by PASCO scientific. Responsibility for the return of equipment for warranty repair belongs to the customer. Equipment must be properly packed to prevent damage and shipped postage or freight prepaid. (Damage caused by improper packing of the equipment for return shipment will not be covered by the warranty.) Shipping costs for returning the equipment after repair will be paid by PASCO scientific. Credits Author: Mr. Jim Housley Equipment Return If the product needs to be returned to PASCO scientific for any reason, notify PASCO scientific by letter, phone, or fax BEFORE returning the product. Upon notification, the return authorization and shipping instructions will be promptly issued. NOTE: NO EQUIPMENT WILL BE ACCEPTED FOR RETURN WITHOUT AN AUTHORIZATION FROM PASCO. When returning equipment for repair, the units must be packed properly. Carriers will not accept responsibility for damage caused by improper packing. To be certain the unit will not be damaged in shipment, observe the following rules: ➀ The packing carton must be strong enough for the item shipped. ➁ Make certain there are at least two inches of packing material between any point on the apparatus and the inside walls of the carton. ➂ Make certain that the packing material cannot shift in the box or become compressed, allowing the instrument come in contact with the packing carton. Address: PASCO scientific Foothills Blvd. Roseville, CA Phone: (916) FAX: (916) techsupp@pasco.com Web: i

4 A Hydraulic/Pneumatic System Manual Table of Contents Section... Page Copyright and Warranty, Equipment Return...i Equipment... 2 Introduction... 3 Apparatus Setup... 4 Connecting the Tubing to the Hydraulic Pump... 4 Bleeding the Hydraulic System... 4 Using with PASCO Pressure Sensors... 5 Experiments: Experiment 1: The Hydraulic Jack as a "Force Transformer" Experiment 2: Relating Force, Pressure, and Area Experiment 3: Understanding Boyle's Law Teacher's Guide Troubleshooting Technical Support... Inside Back Cover 1

5 Hydraulic/Pneumatic System Manual A Equipment The Transparent Devices SE-8764 Hydraulic/Pneumatic Set includes a rugged stand that holds a large cylinder-and-piston syringe, four smaller syringes, tubing assemblies with valves and quick-connect fittings, and this manual. Equipment Included: (a) 1 Jack Stand (Blue Melamine Board) (b) 1 Plunger (piston) with Blue Melamine Platform (c) 1 60 cc Syringe Body (cylinder) (d) 1 Hose assembly (include two one-way valves, tee, and 2 quick-connect fittings) (e) 1 Unattached tee (f) 1 Hose with two quick-connect fittings (g) 1 Unattached valve (h) 1 Hose with 1 quick-connect fitting (i) 1 Hose assembly with tee (for use with optional pressure sensor) (j-m) 4 Syringes (3 cc, 6cc, 12 cc, 20 cc) Additonal Equipment Recommended (for experiments): DataStudio, version 1.5 or later CI-6532A Absolute Pressure Sensor ScienceWorkshop Interface (700, 750, 500 or 300) Computer Stack of 4-6 Books Plastic or Glass Beaker (a) (b) (c) (i) (d) (e) (f) (k) (j) (l) (g) (m) (h) 2

6 A Hydraulic/Pneumatic System Manual Introduction Description The Transparent Devices Hydraulic/Pneumatic Set includes a rugged stand that holds a large cylinder-and-piston syringe, four smaller syringes, tubing assemblies with valves and quick-connect fittings, and this manual. This set makes possible a number of teacher demonstrations and student experiements involving fluids: The operation of a pump The hydraulic/pneumatic jack as a force transformer (simple machine) The difference in compressibility of gases compared to liquids Force, area, and the concept of pressure The study of Boyle's law, using air or other gases Safety Precautions Please teach and expect safe behavior in your classroom and lab. Have students wear safety glasses when working with liquids, glassware, or fragile equipment. Do not use the Hydraulic/ Pneumatic System with corrosive gases. Care and Use of the Apparatus Some simple precautions will help ensure that this set provides years of use: When lifting a load, such as a stack of books, center the load. Do not lift too heavy a load with the piston, and do not lift the load above the 40 cc mark on the syringe. If lubrication of the syringes is needed, use only glycerine or silicone oil. Do not use petroleum-base lubricants, as this will quickly damage the seals. If needed, clean only with a damp rag with a mild, non-abrasive cleaner. Do not immerse the blue melamine board parts in water. Use only light finger pressure on the quickconnect fittings. Do not overtighten. If the apparatus becomes lost or damaged, order a replacement part. 3

7 Hydraulic/Pneumatic System Manual A Apparatus Setup Connecting the Tubing to the Pump 1. Connect the hose assemblies and associated parts in the order (d)-(e)-(f)-(g)-(h), as shown on the previous page. Optional: [If installing a pressure sensor, connect part (i) between parts (f) and (g). Then connect the pressure sensor to the sidearm of part (i).] Note: The quick-connect fittings only require a fraction of a turn with light finger pressure. Do not overtighten. 2. Install the 60 cc syringe (c) in the Jack stand (a), with the graduations visible from the front. Then rotate the syringe one-third turn counterclockwise. Bleeding the Hydraulic System and Observing the Action of the Pump 1. Place the unattached ends of the tubing (d) and (h) in the bottom of a beaker or similar container of water. Keep the valve open (on) with the handle in line with the tubing, as shown in Figure Pull out the small syringe to the limit of the measuring graduation marks. Push it all the way in. Repeat this several times, watching the movement of the fluid and air bubbles. Make sure the ends of the tubing do not come out of the water. 3. Place the sidearm of the tee (e) up through the hole in the bottom of the stand (a) and onto the end of the syringe (c). Turn the syringe one-third clockwise to connnect the to the syringe. Do not overtighten. Insert the piston (b) into the syringe. Push it all the way into the syringe. 4. Install the 6 cc syringe onto the sidearm of the tee of part (d). Do not overtighten. Note: If using the apparatus with air or other gases, the setup is complete. If using the unit with water, as a hydraulic system, or to obtain a better understanding of pump action, continue with the following steps for bleeding the system. Figure 1 3. Describe the fluid movement during the pull stroke. 4. Describe the movement during the push stroke. 5. Close the valve (g) by turning the handle onequarter turn, so that the handle is at right angles to the tubing. Pump the small syringe 3 to 4 times. Tell what happens and why. 6. Without allowing the ends of the tubing to come out of the water, turn the main piston and cylinder assembly upside down. 4

8 700 kpa MAX DRY AIR ONLY CONNECTOR: PASCO PART NO CI-6532A kpa (ABSOLUTE) C A Hydraulic/Pneumatic System Manual Apparatus Setup 7. Open the valve, push in the main piston to expel any air, and close the valve. Return the main piston and cylinder assembly to its normal upright position. The process of eliminating air from a hydraulic system is called "bleeding the system." Using the Pressure Sensors with the Hydraulic/Pneumatic System The PASCO CI-6532 Absolute Pressure Sensor may be connected by first installing hose assembly (i) between parts (f) and (g). After connecting the tubing securely to the pressure sensor, push the open end onto the sidearm of the tee of part (i). CAUTION! Take the following precautions if using the Absolute Pressure Sensor when water is in the system, since the sensor may be damaged by exposure to water. Do not loosen the connection to the pressure sensor while the tube is connected to the hydraulic system. Elevate the pressure sensor above the hydraulic system. Do not leave the pressure sensor connected to the hydraulic system for extended periods. Before storing the sensor, disconnect the hose from the sensor. Pressure in fluids is commonly specified as either absolute pressure or gauge pressure. Absolute pressure considers the entire pressure of the fluid. The CI-6532 Absolute Pressure Sensor measures absolute pressure directly. When the tube of the sensor is not connected to anything, the sensor will output a value around 100 kpa. This is typical atmospheric pressure (near sea level) and varies from day to day, as well as with altitude. Only with the sensor connected to an evacuated space will the sensor output a value near zero. Absolute pressure is measured in Experiment 3. Often, we only want to know how pressure differs from atmospheric pressure. This is called gauge pressure. The Absolute Pressure Sensor may be used to measure gauge pressure by subtracting that day's atmospheric pressure from the direct output of the sensor. Local atmospheric pressure may be determined in advance by reading the sensor output before it is connected to the system. DataStudio may be set to automatically subtract this value to produce gauge pressure readings. Gauge pressure is the quantity studied in Experiments 1 and 2. CAUTION! Do not use the PASCO CI-6534 Low Pressure Sensor with the Hydraulic/Pneumatic System. It is designed to measure pressures much less than generated with this apparatus and will be damaged!!! PRESSURE PORT MATING PRESSURE SENSOR Figure 2 5

9 Hydraulic/Pneumatic System Manual A Experiment 1: The Hydraulic Jack as a "Force Transformer" Equipment Required: Hydraulic/Pneumatic System (SE-8764) Ruler Stack of books Beaker of water Force Sensor (CI-6746 ir CI-6537)* DataStudio, version 1.5 or later ScienceWorkshop interface (700, 750, 500 or 300)* Spring scale (SE-8718) or balance (SE-8758)** * Optional: The Force Sensor, DataStudio, and a ScienceWorkshop interface are recommended, but not required for the experiment. If using the Force Sensor, you must have DataStudio and a ScienceWorkshop interface. ** A spring scale or balance is not needed if a Force Sensor is available. Theory Machines such as levers, pulley arrangements, and hydraulic systems can multiply an input force, to produce a greater output force. In this experiment, we will investigate this phenomenon with a hydraulic jack. The amount that the force is multiplied, FORCE in =FORCE out, is called the actual mechanical advantage (A.M.A.) of the system. Such a system does not multiply input work. Ideally, the input work and output work will be equal. In actual practice, the output work will be somewhat less due to friction. The ratio WORK out / WORK in is called the efficiency of the system. Figure 1.1 In the ideal case of no friction, WORK in = WORK out Substituting the formula for work, Eq1: (FORCE in) X (DISTANCE in) = (FORCE out ) X (DISTANCE out ) Simple algebra can transform this equation into Eq2: (FORCE out ) = (DISTANCE in ) (FORCE in ) (DISTANCE out ) The left side of equation 1 is the actual mechanical advantage (AMA). The right side is called the ideal mechanical advantage (IMA). In the ideal case, where friction is negligible, the IMA is the useful value. The IMA may be used as an estimate of the AMA, assuming the system has a high efficiency. Procedure -- Part 1 1. Set up and bleed the apparatus (as described on pages 4-5). Push the large piston all the way down. Install the 6 cc syringe as indicated in Figure 1.1. Its piston should be pulled out to the largest volume graduation mark. The valve should be closed (handle at right angles to the tubing). 2. Make a stack of 4-6 books and find the weight in newtons. This is Force out. A Force Sensor, spring 6

10 A Hydraulic/Pneumatic System Manual Experiment 1 (Continued) scale, or balance may be used to find the weight. If a balance is used, you will need to calculate the weight. 3. Carefully balance several large books (4-6) on the platform of the large piston. Note: Keep the position the books centered, and do not lean them in any direction. Do not exceed a load of more than six books. CAUTION! To prevent breakage, do not pump the piston above the 40 cubic centimeter mark at any time during the experiment. 4. Push in the piston of the small syringe and notice the amount of force required. In words, compare the force you used to the amount of force required to lift the books directly. 5. Compare the distance you moved the small piston to the distance the books were lifted. 6. Pump the piston of the small syringe several times. Record your observations. 7. Open the valve by turning the handle to line up with the tubing. What happens to the load of books? Why? Procedure - Part II Next, you will make measurements to quantify these observations. Record your measurements in Table 1.2. Measure the distance the small piston moves as you move it from a starting position at the largest graduation mark to the zero mark. Use a ruler, not the graduations on the syringe. This is Distance in. 1. Pull out the small piston to the largest graduation mark. Measure the force required as you push in the piston. Use a Force Sensor if available. If not, use another method, such as holding the syringe vertical and piling on stackable lab weights. This result, expressed in newtons, is Force in. Record this measurement in Table Open the valve to lower the load. Close the valve again. 3. Note the position of the large piston that supports the books. Pump the small piston for several strokes. Count the strokes, and use a ruler to measure the distance the piston moved. Also note the volume of fluid that entered the syringe. Divide the distance by the number of strokes to find the distance out for 1 stroke. Also divide the volume by the number of strokes to find the volume of fluid that entered the large syringe from 1 stroke. 4. Repeat the above measurements for some or all of the other small syringes, as directed by your instructor. 7

11 Hydraulic/Pneumatic System Manual A Experiment 1 (Continued) Data and Calculations Find the inside diameters of each syringe and the areas of circles of these diameters. Express the areas in square meters. Do this by removing the pistons, measuring the inside diameters, and then calculating the areas. Record your results in Table 1.1 Note: A more accurate method is to measure the length of the graduated portion of the syringe, and note the volume of that portion. A formula for the volume of a cylinder, Volume = Area x Length allows calculation of the area. The diameter may be calculated from the area. Table 1.1 Syringe Diameter Length Area Volume (cm) (cm) (m 2 ) Note: Remember to convert cm to meters (1 cc = cm 3 ; 100 cm = 1 m) In Table 1.2, Force in and Distance in are the force and distance involved in operating the small syringe. Force out is the weight of the stack of books, and Distance out is the distance they were lifted as a result of one stroke of the small piston. Explanations for calculating work, the actual mechanical advantage (AMA), the ideal mechanical advantage (IMA), and efficiency may be found in your textbook or in another reference. Table 1.2 Syringe Force in Distance in Force out Distance out AMA IMA Work in Work out Efficiency 8

12 A Hydraulic/Pneumatic System Manual Experiment 1 (Continued) Questions 1. What are some examples of hydraulic systems being used in industry or everyday life? 2. Find the AMA, IMA, Work in, Work out, and the efficiency for each system tried. 3. Which is larger, the AMA or the IMA? Why is this true? Under what sort of ideal conditions would the AMA and IMA be the same amount? 4. Consider the cylinder diameter, cylinder cross sectional area, volume of fluid transferred, and the forces and distances. Which of these is the same for the small and large syringe? 5. The ratio of the two distances can be used to calculate the IMA. What other ratio of items in question 4 gives the IMA? 6. Is the efficiency different for different systems? If so, is there a trend? 7. There are two ways to calculate the efficiency from the preceding values in the table. What are they? 9

13 700 kpa MAX DRY AIR ONLY CONNECTOR: PASCO PART NO Hydraulic/Pneumatic System Manual A Experiment 2: Relating Force, Area and Pressure in a Hydraulic System Equipment Required: 1 Hydraulic/Pneumatic System (SE-8764) Absolute Pressure Sensor (CI-6532A)* DataStudio, ver or later Stack of books ScienceWorkshop interface* Beaker of water Ruler Force Sensor (CI-6746)* or CI-6737 * Optional: The Absolute Pressor Sensor and Force Sensor are recommended, but not required. If using either sensor, you will also need DataStudio and a ScienceWorkshop interface. Theory In this experiment, you will apply force to four different syringe pistons, producing the same pressure each time. The amount of pressure created will be just the amount needed to lift a stack of books on the hydraulic jack, and is the same each time. Each syringe piston has a different cross-sectional area, and requires a different force to produce the required pressure. The constant pressure is established by the weight of the books stacked on the platform of the large syringe. The force, area, and pressure are related by a simple formula that may be discovered using this apparatus. Figure 2.1 Procedure 1. Set up and bleed the system as described on pages Carefully balance several large books on the platform of the large piston. Take care to position the books so that the do not lean in any direction. (d) (e) (i) (f) PRESSURE PORT MATING CI-6532A PRESSURE SENSOR kpa (ABSOLUTE) CAUTION: To prevent breakage, do not pump the piston above the 40 cubic centimeter mark at any time during the experiment. (h) (g) 3. If a PASCO CI-6532A Absolute Pressure Sensor is available, first take a reading with the tubing open to the atmosphere. The result is the present atmospheric pressure at this location. Subtract this value from all of the following pressure measurements to obtain the gauge pressures. Figure Connect the sensor to the sidearm tee of part (i), which is connected between parts (f) and (g), as shown in Figure 2.2. CAUTION: The following precautions must be taken if the Pressure Sensor is to be used when water is in the system, since the sensor may be damaged by exposure to water. Do not loosen the connection to the pressure sensor while the tube is connected to the hydraulic system. (See the next page for more necessary precautions.) 10

14 A Hydraulic/Pneumatic System Manual Experiment 2 (Continued) SENSOR PRECAUTIONS (continued) Elevate the Pressure Sensor above the hydraulic system. Do not leave the Pressure Sensor connected to the hydraulic system for extended periods. Before storing the sensor, disconnect the hose from the sensor. 5. With the smallest piston installed at point (d), measure the force required to push in the plunger and lift the stack of books. Use a CI-6746 Force Sensor if available. If not, use another method such as holding the syringe vertical and piling on stackable weights. 6. Repeat the above steps for as many of the four small syringes, as time allows. Data and Calculations Find the cross-sectional area of the small syringe. This may be done by measuring the inside diameter of the syringe, and using the formula for the area of a circle. (Note: A more accurate method is to use a ruler to measure the graduated portion of the syringe, and to note the volume of that portion.) A formula for the volume of a cylinder, Volume = Area x Length allows calculation of the area. The diameter may be calculated from the area. Convert the area to square meters. Record the pressure if a Pressure Sensor is available. Table 2.1 Syringe Stacked Weight Force (N) Area (m 2 ) Gauge Pressure (Calculated)(N/m 2 ) Gauge Pressure (Sensor) (kpa) 1. Make a graph displaying the (area, force) data pairs from the four small syringes. Area should be plotted along the horizontal axis, and force along the vertical axis. 2. A straight line passing through the origin should show the pattern of the data. Use software such as DataStudio, or traditional techniques, to determine the slope and the equation of this best-fit line. 3. Calculate the pressure by considering the weight of the books and the area of the piston supporting them. Make the necessary measurements, and calculate the pressure in Newtons/square meters. 11

15 Hydraulic/Pneumatic System Manual A Experiment 2 (Continued) Questions 1. Compare the formula for pressure to the formula for the slope of the graph you created. 2. Why did we believe each syringe would produce equal pressure in this experiment? 3. How does the linear graph of this experiment relate to pressure? 4. PASCO's pressure sensors produce pressure readings in kpa (kilopascals). How is a pascal defined in terms of other common metric units? 5. The pressure calculated using force and area measurements was somewhat greater than that calculated using the weight of the books on the large piston or that measured by the sensor. Why was that true? 12

16 700 kpa MAX DRY AIR ONLY CONNECTOR: PASCO PART NO C A Hydraulic/Pneumatic System Manual Experiment 3: Understanding Boyle's Law Equipment Required: Hydraulic/Pnuematic System (SE-8674) Glycerine or Silicone oil DataStudio, version 1.5 or later* ScienceWorkshop interface* Stack of Books Absolute Pressure Sensor (CI-6532A)* Balloons Ruler *DataStudio, a ScienceWorkshop interface, and Absolute Pressure Sensor are recommended, but not required. Purpose: Unlike liquids, which have a relatively constant volume, a sample of gas may vary greatly in volume. The volume and pressure are related by a mathematical formula, called Boyle's law. This lab provides data that may be analyzed to discover this formula. Air or another gas may be used. Procedure: 1. Set up the system (as described on pages 4-5). Keep the system free of water, as much as possible. (see setup in Figure 3.1) (f) 2. Attach any small syringe to the sidearm of the tee part (s). If possible, arrange to use a pressure sensor. The sensor attaches to the sidearm of part (i). Part (i) attaches between parts (f) and (g). (Figure 3.1) (d) (i) (g) PRESSURE PORT MATING CI-6532A PRESSURE SENSOR kpa (ABSOLUTE) Note: If you are not using a pressure sensor, lubricating the large syringe is important. Use glycerine or silicone oil. To avoid damaging the seals, do not use a petroleumbased lubricant. Figure Close valve (g) by turning the handle at right angles to the tubing. If using a gas other than air, connect a balloon containing the gas to the unattached end of the hose assembly (d). If using air, leave the end unattached. 4. Now pump the small syringe until the large syringe piston goes up to the 20 cc mark. Open the valve while pushing the large syringe platform down, and then close the valve again. This expels any gas previously used. Use the small syringe to pump the large syringe piston up to the 50 cc mark. 5. If a pressure sensor is being used, you may skip this step. If no pressure sensor is available, find the weight of the books in newtons. Hang them from a force sensor or spring scale using a loop of string. Alternately, a balance may be used to find mass and the weight calculated. Much effort will be saved if identical books can be used. Otherwise, you will need to weigh and record the weight of each book, (and carefully document the order that you stack the books on the platform in step 6). 6. Add one textbook to the platform at a time, carefully centering and balancing the stack each time. After adding each textbook, wait a minute for the volume and pressure to stabilize. Then record the volume of the gas in the large syringe. If a pressure sensor is being used, also record the pressure under the column "Total Pressure." The columns, "Total Weight of Books" and "Pressure due to 7. If no pressure sensor is available, an additional step may increase your accuracy. Remove the books, one by one, and record the volumes and total weight of the remaining books after each book is removed. 13

17 Hydraulic/Pneumatic System Manual A Experiment 3 (Continued) Calculations and Analysis Boyle's law states that the pressure of a gas sample times its volume is constant, assuming a constant temperature. If you used a pressure sensor, you can test this by calculating P x V for the gas sample for each of the six pressures. Then you can skip ahead to the questions. Table 3.1 Number of Books Volume (cc) Total weight of books (N) Pressure due to books (kpa) Total Pressure (kpa) P x V If you don't have pressure data, proceed to the next steps. Your volume readings, as you stacked the books on the piston, are likely too large. The corresponding readings, as you removed the books from the piston, are likely too small. (Do you see why?) Average the two volumes for one book, the two volumes for two books, etc., and enter the average values into the table. The pressure due to the weight of the books may be calculated by the formula, Pressure=force/area The force is the weight of the books. Area is the area of the circular end of the piston, 5.51 x 10-4 m 2. Calculate these pressure values and enter them into the table under "Pressure due to books." The total pressure of the gas sample is greater than this because the earth's atmosphere presses down on the syringe. At sea level, on a typical day, this pressure amounts to 101 kpa, or 101 x 10 3 N/m 2. In Table 3.1, add this value to the values in the "Pressure due to books" column to give the values for the "Total Pressure" column. If you know the actual atmospheric pressure for your location, use that value instead. Boyle's Law says that the product of pressure and volume for a gas sample is constant if temperature is constant. Calculate P x V for each of the rows of the table. Do the results agree with Boyle's Law, considering uncertainty? 14

18 A Hydraulic/Pneumatic System Manual Experiment 1: Teacher's Guide Procedure Notes and Observations: 4. The force required to lift the books on the hydraulic system is much less than if you were to lift the books directly. 5. The distance the small piston moves is much greater than the distance the books are lifted. 6. Pushing the syringe pushes the water toward the large piston. Pulling the syringe out creates a suction that pulls water from the beaker into the syringe. If the open tubing ends are not completely submerged in the container of water, air will enter the system. 7. Opening the valve reduces the pressure in the hydraulic system. The large piston falls back to the baseline (zero mark.) The water from the large syringe travels through the valve and into the beaker. Sample Data Syringe Diameter(m) Length (m) Volume 3 cc 6 cc 12 cc 20 cc 60 cc 8.83 x 10-3 m 1.26 x 10-2 m 1.56 x 10-2 m 2.00 x 10-2 m 2.65 x 10-2 m Area (m 2 ) 6.12 x 10-5 m x 10-4 m x 10-4 m x 10-4 m x 10-4 m 2 Syringe Force in (Newtions) Distance in (m) Force out (Newtons) Distance out (m) AMA IMA Work in (Joules) Work out (Joules) Efficiency (%) 3 cc 6 cc 12 cc 20 cc % 68% 75% 78% 15

19 Hydraulic/Pneumatic System Manual A Experiment 1: (Results Continued): Answers to Questions: 1. Some examples of hydraulic systems used in industry include hydraulic brakes in automobiles, hydraulic jacks to lift cars, and hydraulic presses. 2. The ideal mechanical advanatage (IMA) is always larger because the IMA assumes there are no forces working against the machine under study. The actual mechanical advantage and IMA are equal where friction (such as the friction working between the plunger and the syringe cavity), dissipation of thermal energy, water turbulence and air resistance (such as bubbles) are negligible. In the ideal condition, there is no wasted energy or work. 3. The only parameters that are the same for the small and large syringe are the force per unit area and the volume of liquid transferred. 4. The ratio of the areas of the large and small cylinders can also be used to calculate the IMA. 5. Yes, the efficiency is different for different systems. In general, the efficiency increases when you go up in syringe size because less strokes (and thus work) are required to move the piston in the apparatus upward. Also, friction may be a smaller percentage of the total Force in. 6. The two ways to calculate efficiency are Work out /Work in and AMA/IMA. Experiment 2: Data and Calculations 1. The graph will show the force increasing linearly with the area. (This is true while the pressure remains constant.) 2. The slope is approximately constant. The pressure was also constant in this experiment. (Note: In some cases, due to experimental error, there may be some small fluctuations in the pressure.) 3. Pressure=Force/Area; (example: 36.44/5.51 x 10-4 = 66,100 N/m 2 = 66.1 kpa) Sample Data Syringe Volume 3 cc 6 cc 12 cc 20 cc 60 cc Length (m) m m m m m Area (V/L) (m 2 )* 6.12 x 10-5 m x 10-4 m x 10-4 m x 10-4 m x 10-4 m 2 *Note: Remember to convert your units to meters. (1 cc = 1 cm 3; 100 cm = 1 m ) 16

20 A Hydraulic/Pneumatic System Manual Experiment 2 (Results Continued): Syringe Stacked Masses (kg) Force Applied by Masses or Sensor (N) Area (m 2 ) Gauge Pressure (Calculated) (N/m 2 ) Gauge Pressure (Sensor) (kpa) 3 cc 6 cc 12 cc 20 cc N 13.6 N 19.0 N 30.5 N 6.12 x 10-5 m x 10-4 m x 10-4 m x 10-4 m x x x x kpa 82 kpa 82 kpa 82 kpa Answers to Questions 1. The two formulas are essentially the same! 2. Each syringe was used to produce just enough pressure to lift the stack of books. The same amount of pressure is needed to lift the stack every time. 3. The slope of the graph, which is constant, should be equal to the pressure, which is also constant kpa = 1000 Pa (1 Pa is defined as 1 N/m 2 ). 5. Part of the force applied serves to counteract friction. If friction could be eliminated, slope and pressure would be equal. Experiment 3: Data and Calculations (Typical results) Number of Books Volume (cc) Total Weight of Books (N) Total Pressure (kpa) Pressure x Volume cc 43 cc 37 cc 33 cc 29 cc 22 cc

21 Hydraulic/Pneumatic System Manual A Troubleshooting Problem: The piston in the Hydraulic/Pneumatic apparatus does not move up when I apply pressure to the syringe. Solution(s): Check the following: a) Ensure that tee is attached under the bottom of the stand. If the tee becomes loose, disconnected or mislodged, the hydraulic system is no longer closed to the atmosphere, and water may begin to slowly run out. b) Check to ensure that the valve is closed while you are pushing on the syringe. Problem: The results for pressure do not appear accurate for the volume reading. Solution(s): a) Before and after changing syringes, ensure that you properly bleed the apparatus (see page 4-5 of this manual for instructions on bleeding the apparatus). b) Take all volume readings from the same position on the point or bottom of the syringe. For example, if you take your first reading from the second line on the black plunger, take all subsequent syringe readings on the second line on the black plunger. c) If desired, you may calibrate the sensors. Follow the instructions in the DataStudio online help. Problem: Too many air bubbles are in the hydraulic system. Solution(s): Follow the instructions for bleeding the system on pages 4-5 of this manual. Ensure you bleed the system with the valve opened, closed, and also with the apparatus upside down. Problem: When I apply pressure with the syringe, the large piston pops out. Solution(s): Use a smaller syringe or take smaller strokes with the syringe. The larger 20 cc syringe intakes and moves a greater volume of water through the large piston than the smaller syringes. With the large syringe, it's possible to pop the piston out with just 3 strokes. Problem: I want to use the system with air (or another gas), but the tubing is wet. Solution(s): Follow the instructions on pages 4-5 for bleeding the system. While bleeding, have a dry, empty container available and place the open ends of the tubing in the container to collect any water. If available, use a small air-dry vacuum or blow dryer to suck out or eliminate moisture in the tubing. 18

22 A Hydraulic/Pneumatic System Manual Notes 19

23 Hydraulic/Pneumatic System Manual A Technical Support Feedback If you have any comments about the product or manual, please let us know. If you have any suggestions on alternate experiments or find a problem in the manual, please tell us. PASCO appreciates any customer feedback. Your input helps us evaluate and improve our product. To Reach PASCO For technical support, call us at (toll-free within the U.S.) or (916) Fax: (916) techsupp@pasco.com Web: Contacting Technical Support Before you call the PASCO Technical Support staff, it would be helpful to prepare the following information: If your problem is with the PASCO apparatus, note: - Title and model number (usually listed on the label); - Approximate age of apparatus; - A detailed description of the problem/sequence of events (in case you can t call PASCO right away, you won t lose valuable data); - If possible, have the apparatus within reach when calling to facilitate description of individual parts. If your problem relates to the instruction manual, note: - Part number and revision (listed by month and year on the front cover); - Have the manual at hand to discuss your questions. 20

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