PASCO Specialty & Mfg. ME-8930 User's Manual
Contents
1. eee 19 Experiment Four Conservation of Angular Momentum esee 25 Other Suggested Experiment aasa BAN iter e e DIR e AGA desde 3l Technical Support 2ang KA back cover PASC CN i scientific Copyright Warranty and Equipment Return Please Feel free to duplicate this manual subject to the copyright restrictions below Copyright Notice The PASCO scientific 012 06734A Smart Timer 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 11 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 c2. N to Smart Timer channel 1 or 2 steel ball support rod M and base receptor pad Figure 10 1 Setup for determining the acceleration due to gravity with the ME 9207B Free Fall Adapter To Smart Timer channel 1 or 2 G M Tube P Supply Figure 11 1 Setup for counting radiation with the SN 7927 G M Tube Power Supply Technical Support Feedback Contacting Technical Support 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 1 800 772 8700 toll free within the U S or 916 786 3800 fax 916 786 3292 e mail techsupp pasco com web WWW pasco com Before you call the PASCO Technical Support staff it would be helpful to prepare the following information gt 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 gt If your problem relates to the instruction manual
3. Equal Masses a Place one cart at rest in the middle of the track Give the other cart an initial velocity toward the cart at rest b Start both carts at opposite ends of the track at approximately the same speed Unequal Masses Put two mass bars in one of the carts so that the mass of one cart 3M is approximately three times the mass of the other cart 1M Weigh the carts and record the masses in Table 3 3 a Place the 3M cart at rest in the middle of the track Give the 1M cart an initial velocity toward the cart at rest b Start the carts at opposite ends of the track at approximately the same speed toward each other c Start cars at the same end with the 3M car ahead of and moving slower than the 1M car Note Do each experiment at least 3 times Table 3 3 Data Cea eu ICE LE LLL a LLL Trial 3 Trial 4 Trial 5 Trial 6 Trial 7 22 PA 0 012 06734A Smart Timer Table 3 4 Results Indie nr AAA li EE pues ii 1 pap E EEE A ETA Questions 1 Kinetic energy is not conserved in inelastic collisions but it is conserved in ideal elastic collisions For one of the collisions calculate the percentage of the kinetic energy that 1s lost in the collision Was kinetic energy conserved Explain your results PASC 23 Smart Timer 012 06734A 24 012 06734A Smart Timer Experiment Four Rotational Inertia of a Disk and Ring EQUIPMENT REQUIRED Rotating Platform M
4. and allow you to change the measurement type input channel 2 input channel 1 Figure 2 Connecting the photogate to the Smart Timer gt Note Smart Timers shipped to certain locations are supplied with a transformer for 220 240 VAC 50 Hz power gt Important Setup Note The Smart Timer incorporates a feature to increase the battery lifetime The photogate turns on only when Start Stop is pressed to start an experiment Photogate power is turned off when the measurement is complete or the operator presses Start Stop The exception is the Test mode in which photogate power is turned on as soon as the display reads Test Gates and is not turned off until Select Measurement is pressed again Setup for the experiment is often best accomplished in Test Gates mode Smart Timer Modes of Operation The Smart Timer has 18 modes of operation organized into five groups Time Speed Acceleration Counts and Test A 012 06734A Smart Timer Quick Cross Reference for Suggested Activities and Smart Timer Modes Fence Mia Use time measurements to determine the calculate the acceleration ofa launch speed of cart or the a ball acceleration due to gravity ofa Picket Fence Stopwatch Time students running Measure the period of a pendulum Use the time measurement to Use the time measurement to calculate the speed of a cart Operate Free Fall Adapter and L
5. Instruction Manual and 012 06734A Experiment Guide for the 09 98 PASCO scientific Model ME 8930 SMART TIMER 1998 PASCO scientific BY Ga 10101 Foothills Blvd Roseville CA 95747 7100 scientific Phone 916 786 3800 FAX 916 786 8905 e www pasco com 012 06734A Smart Timer Table of Contents Section Page flde ENSS i Copyright Warranty and Equipment Return eese nennen ii A E RN 1 EQUIP aiii is Alala ina 3 Operating the Smart TIMET sretan treten een 4 Smart Timer Modes of Operation seekers iisi erei e r na a a Tn iei 4 Quick Cross Reference for Suggested Activities and Smart Timer Modes 5 A 6 Speed Measurement Modes naaa ALA NAGANA 7 Table 1 Summary of Timing Modes sse 8 9 Acceleration Measurement Modes essent 10 Count Modes ene I tetendit b e teet e deiade tem etre 10 TestMode REE 11 A anan tanah 11 FOCK uid M M Em 11 Caring forthe Smart Tier iei te ier titi 12 O 12 Accessory OPlONS areas ute ern Ber reger a kreis ee 12 Troubleshooting u data ALINA AIRA ANGARA idad 14 Experiment One Acceleration of Gravity eese rennen enne 15 Experiment Two Newton s Second Law essere nre 17 Experiment Three Conservation of Momentum In Collisions
6. note Part number and revision listed by month and year on the front cover Have the manual at hand to discuss your questions
7. cleared and the reappears This RESET START STOP sequence is repeated for Note each new elapsed time Whenever the is not showing the mode may be The stopwatch changed function is not a Using the Alternate Timing Function Connect an appropriate accessory to input precision nming channel 1 or 2 Enter Stopwatch mode and press the Start Stop key The Smart mode and is Timer will beep and a will appear on the second line of the LCD At this time therefore most the accessory will be powered By blocking and unblocking the beam in the case of useful for events the Laser Switch or by dropping the steel ball in the case of the Free Fall Adapter the elapsed time will be measured The Smart Timer will resolve 100 microseconds that are longer than one second in the alternate timing mode The accuracy of the stopwatch is gt Notes about the Stopwatch Mode 10 1 Although it is possible to use older style fences in the alternate timing function to milliseconds obtain photogate beam block times the Smart Timer will provide much higher accuracy when used with the included fences and the standard timing modes gt Hint 2 Two photogates cannot be plugged into the Smart Timer when you are using a ue For easier photogate to start and stop the timer A single photogate can be plugged into channel 1 or 2 to start and stop the timer But if two photogates are plugged in when one gate is blocked the other gate i
8. 3 Step Pulley about which the thread is wound and T is the tension in the thread when the apparatus is rotating Applying Newton s Second Law for the hanging mass m gives See Figure 4 2 ZF mg T ma Smart Pulley See ease Pd d Fr T rotational disk L A base n hanging mg Figure 4 2 Rotational Apparatus and Free Body Diagram Solving for the tension in the thread gives T mg a Once the linear acceleration of the mass m is determined the torque and the angular acceleration can be obtained for the calculation of the rotational inertia 26 PA 0 012 06734A Smart Timer Setup 1 2 3 Place the disk directly on the center shaft as shown in Figure 4 3 The side of the disk that has the indentation for the ring should be up Place the ring on the disk seating it in this indentation Mount the Smart Pulley to the base and connect it to channel 1 or 2 of the Smart Timer Procedure Measurements for the Theoretical Rotational Inertia 1 Weigh the ring and disk to find their masses and record these masses in Table 4 1 2 Measure the inside and outside diameters of the ring and calculate the radii R and R Record in Table 4 1 3 Measure the diameter of the disk and calculate the radius R and record it in Table 4 1 Table 4 1 Theoretical Rotational Inertia Data Mas
9. Photogate Dynamics Head Cart To Smart Timer Photogate mounting bracket p a Figure 5 1 Setup for the Acceleration Down an Incline Experiment Photogate To Smart Timer Head ME 9471 Super Pulley Picket Fence 9QooooQooOooQOopODOQQO ESTO spring E E QQQQQQ x I Cw 3 Mass and Hanger te Figure 6 1 Setup for the Simple Harmonic Oscillator Experiment 31 Smart Timer 012 06734A 32 Oscillations on an Incline Experiment 4 Use a photogate and the Smart Timer instead of a stop watch and use the ME 9471 Picket Fence ME 9471 spring part number 648 04704 not the Picket Fence Smart Timer Picket Fence Figure 7 1 Set up the Smart Timer to measure Time Pendulum Start the cart oscillations and Press activate the Smart Timer to Photogate Mounting Bracket si measure the period of oscillation Figure 7 1 Setup for the Oscillations on an Incline Experiment Springs in Series and Parallel Experiment 5 Use the setup illustrated in Figure 7 1 Set up the Smart Timer to measure Time Pendulum Start the cart oscillations and activate the Smart Timer to measure the period of oscillation Note The following experiment is in copy ready form in the manual for the Introductory Dynamics System with Computer Timing Kit manual number 012 04894 C
10. Projectile A Launcher Use the Smart Timer instead of a yp To Smart Timer channel 2 Photogate Timer and set the Loco am X Photogate NI Mounting Bracket Smart Timer to measure Time Two Gates Be sure the plug M S S x N from the Photogate is connected to channel 1 ofthe Smart Timer and the plug from the Time of SS a Time of Flight di Accessory Flight Accessory is connected to To Smart Timer channel 2 see Figure 9 1 Press channel 1 El to activate the Smart Timer and fire the launcher Figure 9 1 Setup for the Timer of Flight and Initial Velocity Experiment eo 33 Smart Timer 012 06734A 34 Determining the acceleration due to gravity g with the Free Fall Adapter ME 9207B Insert the plug of the Free Fall Adapter into channel 1 or 2 of the Smart Timer Figure 10 1 Set up the Stopwatch mode of the Smart Timer Press EJ once The Smart Timer is now activated and will record the time the interval between the release of the ball and the contact of the ball with the receptor pad of the Free Fall Adapter Counting radiation with the G M Tube Power Supply SN 7927 Insert the plug of the G M Tube Power Supply into channel 1 or 2 of the Smart Timer Figure 11 1 Set up the Smart Timer to measure Counts 30 seconds 60 seconds 5 minutes or Manual Press l to activate the Smart Timer ball release mechanism controller box of the Pa Free Fall Adapter
11. Seconds Other than timing the count interval for 60 seconds the 60 second count mode is the same as the 30 second mode 5 Minutes Other than timing the count interval for 5 minutes the 5 minute count mode is the same as the 30 second mode Manual Manual mode will count high to low voltage transitions on either input and display them on the second line of the liquid crystal display There is no time limit for counting however the upper limit on the number of total counts is still 9 999 999 Each count will be accompanied by a short beep Used with a PASCO SN 7927 G M Tube Power Supply this mode is useful for group demonstrations to show the random nature of atomic disintegration and the inverse square relationship between number of disintegration s detected and distance from the radioactive source Test Mode Gates In the Test Gates measurement the external measuring accessory is powered as long as the top line of the display reads Test Gates This mode is useful for experiment setup or for testing accessory photogates G M tubes or other Smart Timer accessories Pressing the Select Measurement key will exit the test mode and remove power to the external device The display graphics depict a blocked photogate as a vertical line and an unblocked photogate as an arrow Timing Diagrams The timing diagrams on pages 8 and 9 show the interval f that is measured in each timing mode In each diagram an elevated line corresponds to the photoga
12. of approximately 30 g Remove the disk from the shaft and rotate it up on its side Mount the disk vertically by inserting the shaft in one of the two D shaped holes on the edge of the disk See Figure 4 4 Repeat steps and 2 and record the data in Table 4 2 HE a rotational disk D hole of Ek rotational disk u rotating shaft a A base e Al Em ESS U U U U ToT PAE m Figure 4 4 Disk mounted vertically Table 4 2 Experimental Rotational Inertia Data Ring and Disk a Disk Alone Disk Vertical Hanging Mass Hanging Mass Friction Mass Acceleration a Friction Mass 012 06734A Smart Timer Calculations Record the results of the following calculations in Table 4 3 1 Subtract the friction mass from the hanging mass used to accelerate the apparatus to determine the mass m to be used in the equations 2 Calculate the experimental value of the rotational inertia of the ring and disk together 3 Calculate the experimental value of the rotational inertia of the disk alone 4 Subtract the rotational inertia of the disk from the total rotational inertia of the ring and disk Note This calculation will be the rotational inertia of the ring alone 5 Calculate the experimental value of the rotational inertia of the disk about its diameter 6 Calculat
13. E 8951 Ohaus Triple Beam Balance DE 8707 or similar Rotational Inertia Accessory ME 8953 paper clips for masses lt 1 g Smart Pulley ME 9387 calipers Smart Timer ME 8930 Purpose The purpose of this experiment is to find the rotational inertia of a ring and a disk experimentally and to verify that these values correspond to the calculated theoretical values Theory Theoretically the rotational inertia of a ring about its center of mass is given by I M R Ry where M is the mass of the ring R is the inner radius of the ring and R dp is the outer radius of the ring See Figure 4 1a The rotational inertia of a disk about its center of mass Figure 4 1b is given by I MR 2 Figure 4 1a Definition of R and R of a ring where M is the mass of the disk and R is the radius of the disk The rotational inertia of a disk about its diameter Figure 4 1c is given by 1 2 I MR Figure 4 1b Figure 4 1c Disk rotating about its center of mass Disk rotating about its diameter PASC OU 25 Smart Timer 012 06734A To find the rotational inertia experimentally aknown torque is applied to the object and the resulting angular acceleration is measured Since 7 Ja 2 I a where aris the angular acceleration which is equal to a r and ris the torque caused by the weight hanging from the thread that is wrapped around the base of the apparatus T rT where r is the radius of the
14. able 2 1 Calculate the average accelerations and record in Table 2 1 9 Increase the mass of the cart using the bar mass and repeat the procedure Table 2 1 Data cart hanging ave measured theoretical mass m mass m accel 1 accel 2 accel 3 accel force force difference a m m a m g theoretical measured x 100 difference theoretical Analysis 1 Calculate the measured force F m m a and record in Table 2 1 2 Calculate the theoretical force F m g and record on Table 2 1 3 Calculate the percent difference of the theoretical force vs the measured force and record in Table 2 1 Questions 1 Did the results of this experiment verify that F ma Explain 2 Why is the mass in F ma not just equal to the mass of the cart 3 When calculating the force on the cart using mass times gravity why isn t the mass of cart included 4 Discuss the impact on the results of assuming the frictional force to be zero 18 PA 0 012 06734A Smart Timer Experiment Three Conservation of Momentum In Collisions EQUIPMENT AND MATERIALS REQUIRED Smart Timer ME 8930 2 Photogate ME 9498A Collision Cart with mass 2 ME 9454 2 Photogate Bracket Part No 003 04662 Dynamics Cart Track ME 9429A 2 Smart Timer Picket Fence balance Purpose The purpose of this experiment is to show that momentum is conserved in co
15. aser Operate the Switch Time of Flight Accessory Measure one Continuously speed on a Smart monitor angular Pulley speed in conservation of angular momentum experiments Measure the initial and final speeds of two carts during a collision for conservation of momentum Measure the speed of a cart Two Gates Linear Pulley Angular Pulley cm s cm s2 rad s2 p Measure accel eration of a cart at one point on the track Measure the acceleration of a hanging mass in rotational inertia Measure the acceleration of a hanging mass in rotational inertia Measure the average acceleration of a cart over the whole length of the track experiments experiments Measure the accel eration due to gravity g of a Picket Fence Counts for 30 seconds 60 seconds 5 minutes Count blocking events for the specified period of time Measure radiation emission events with the GM Tube Power Supply Smart Timer 012 06734A summary of the mode suggested for a given experimental activity can be found on page 5 Quick Cross Reference for Suggested Activities and Smart Timer Modes Refer to the timing diagrams in Table 1 pages 8 and 9 for a detailed look at how the Smart Timers times events on its input s and an explanation of how speed and acceleration calculations are performed internally The following are detailed descriptions of the Smart Timer s modes of op
16. at the Smart Timer is able to discern between acceleration positive number and deceleration negative number Linear Pulley In this mode the Smart Timer converts rotary motion of a PASCO pulley to an equivalent linear acceleration in cm s Angular Pulley In this mode the Smart Timer converts rotary motion of a PASCO pulley to an equivalent angular acceleration in rad s Two Gates When two photogates are placed an arbitrary distance apart the average acceleration between the two can be calculated In this mode the inputs used are not arbitrary The first photogate to be encountered must be connected to input 1 and the second to input 2 Count Modes 30 Seconds The timed 30 second count mode will count high to low voltage transitions on either input and display them on the second line of the liquid crystal display After the counting period is over the Smart Timer will beep once remove the power to the external device and freeze the display Pressing Start Stop erases the old count and begins a new 10 PASC 012 06734A Smart Timer timing interval If you wish to stop the count during a timing interval press Start Stop The display will freeze the current count and the will disappear from the first column At this time you may select a new measurement or start a new timing interval The maximum counting rate for any of the counting modes is 5 000 counts per second and the maximum count is 9 999 999 60
17. beam is unblocked When an object blocks the beam so it doesn t strike the detector the signal to the timer changes PASC Oe en Smart Timer 012 06734A In One Gate Mode a single photogate lets you measure the time velocity or acceleration of a fence as it passes through the photogate Two photogates are used for collision experiments using one or two carts or for experiments where the velocity of a cart must be measured at two different points In Two Gate Mode two photogates are used and the time to travel between the two can be measured This mode can also be used to measure time of flight using the ME 6810 Time of Flight Accessory Use with the Smart Pulley For rotary motion studies the ME 9387 Smart Pulley available separately is ideal It combines a photogate with a pulley and when used with the Smart Timer allows direct measurement of angular speed and acceleration When used with a string connected to a glide or Dynamics Cart the Smart Timer and Smart Pulley can be used to determine linear acceleration cm s as well gt Note The use of pulleys with different diameters and or different number of spokes than the Smart Pulley or the ME 9450 Super Pulley will give incorrect results in the speed and acceleration calculations Power Options The Photogate Timer can be powered using the included 9VDC adapter It will also run on 4 AA size 1 5 volt alkaline batteries which will provide over 100 hours of operation i
18. c 01 2 06734A Smart Timer Introduction I The PASCO ME 8930 Smart Timer is an accurate versatile digital timer and measurement system for the student laboratory The Smart Timer offers 0 1 ms timing resolution and an easy to use memory function The Smart Timer measures several types of events detected with PASCO s digital sensors including speed and acceleration using standard photogates The PASCO ME 9387 Smart Pulley the ME 9207B Free Fall Adapter the ME 6810 Time of Flight Accessory or the ME 9259A Laser Switch also work with the Smart Timer The Smart Timer counts radiation emission events detected with the SN 7927 G M Tube Power Supply or the SE 7997 G M Tube The Smart Timer features two input channels and a 2 line 16 character alphanumeric liquid crystal display that indicates the operating mode and experimental results Features The Smart Timer s memory function makes it easy to time events that happen in rapid succession such as a Dynamics Cart passing twice through the photogate once before and then again after a collision The 0 1 ms resolution is especially useful in some experiments such as measuring velocity or acceleration during free fall The Smart Timer can calculate velocity before and after a collision between two carts using a single timer With the new fence design and sensing logic parallax errors are eliminated and timing accuracy is improved considerably over existing timing options The Smart T
19. changeably For all other modes see the individual descriptions below Plug the 9 VDC power adapter into the small receptacle on the side of the timer and into a standard 110 VAC 60 Hz wall outlet Position the photogate head so the object to be timed will pass through the arms of the photogate blocking the photogate beam Loosen the clamp screw if you want to change the angle or height of the photogate then tighten it securely Slide the power switch to the ON position The Smart Timer will beep and show PASCO scientific on the display From this point the three step setup of the Smart Timer is easy 1 Press the Select Measurement key until the desired measurement type is displayed on the top line of the display Note that the menu rolls over to the beginning after the last type is selected 2 Press the Select Mode key until the measurement mode is displayed after the measurement type You cannot begin a measurement until both the type and mode have been selected 3 Once a complete measurement has been selected press Start Stop to begin You will hear a beep and a asterisk will appear on the second line of the display In most modes the indicates that the Smart Timer is now waiting for an event to occur like a fence passing through a photogate If an event occurs the Smart Timer beeps again displays a result and the disappears Pressing Start Stop before an event occurs will remove the
20. e the theoretical value of the rotational inertia of the ring 7 Calculate the theoretical value of the rotational inertia of the disk about its center of mass and about its diameter 8 Use a percent difference to compare the experimental values to the theoretical values Theoretical Experimental Rotational Inertia for the Ring and Disk Combined Rotational Inertia for the Disk Alone Rotational Inertia for the Ring Rotational Inertia for the Vertical Disk PASC 29 Smart Timer 012 06734A 30 012 06734A Smart Timer Other Suggested Experiments Note The following experiments are in copy ready form in the manual for the Dynamics Cart Accessory Track Set manual number 012 05035 e Acceleration Down an Incline Experiment 8 Use a Photogate and the Smart Timer instead of a stop watch Figure 5 1 Adjust the height of the Photogate so the light path is intersected with the 5 cm fence of the Smart Timer fences Set up the Smart Timer to measure Acceleration One Gate Press El to activate the Smart Timer and release the cart e Simple Harmonic Oscillator Experiment 3 Use a Photogate and the Smart Timer instead of a stop watch and use the ME 9471 Picket Fence part number 648 04704 not the Smart Timer Picket Fence Figure 6 1 Set up the Smart Timer to measure Time Pendulum Press B to activate the Smart Timer to measure the period of oscillation Smart Timer Picket Fence SY
21. er to measure Speed collision cm s Press fj to activate the Smart Timer gt Note If the flags of both carts do not go through the photogate beams twice the Smart Timer will not complete the timing cycle and display velocities automatically You will need to push EJ to stop timing The completed timing measurements will be displayed and the uncompleted measurements will be registered as 0 Press gg or EJ to view the velocities from photogate 2 You can scroll back and forth between the displayed velocities from photogates 1 and 2 by pressing either of these keys Press EJ to reactivate the Speed collision cm s mode or to change modes 4 Perform each of the following completely inelastic collisions Equal Masses a Place one cart at rest in the middle of the track Give the other cart an initial velocity toward the cart at rest b Start both carts at one end of the track Give the first cart a slow velocity and the second cart a faster velocity so that the second cart catches the first cart Unequal Masses Put two mass bars in one of the carts so that the mass of one cart 3M is approximately three times the mass of the other cart 1M Weigh the carts and record the masses in Table 3 1 a Place the 1M cart at rest in the middle of the track Give the 3M cart an initial velocity toward the cart at rest b Start the carts at opposite ends of the track at approximately the same speed toward each other c Place both cart
22. eration Time Modes One Gate In One Gate mode timing begins when the beam is first blocked and continues until the beam is blocked again This mode can be used to measure the speed of an object as it passes through the photogate If an object of length L blocks the photogate for a time f the average velocity of the object as it passed through the photogate was Lit Fence In Fence mode the timer measures the time between successive interruptions of the photogate Timing begins when the beam is first blocked and continues until the beam is unblocked and then blocked again The Smart Timer can remember ten such interruptions and will allow the user to scroll through the times using either the Select Measurement or the Select Mode keys Pressing the Start Stop once will allow another measurement type to be selected Pressing it twice begins a new Fence Mode measurement Note that once a measurement has begun with an initial block of the photogate the Smart Timer will continue to time until ten interruptions are counted before stopping the measurement and displaying the result Pressing Start Stop will stop the measurement and any recorded times will be displayed Two Gates In this mode the Smart Timer measures the time between blocking two photogates This mode is useful for not only air tracks and Dynamics Tracks but also with the ME 6810 Time of Flight Accessory In this mode you must plug the photogate you expect to encounter first into inp
23. es 16 12 Y 012 06734A Smart Timer Experiment Two Newton s Second Law EQUIPMENT AND MATERIALS REQUIRED Smart Timer ME 8930 Photogate ME 9498A Dynamics Cart ME 9430 or ME 9454 Photogate Bracket part no 003 04662 Dynamics Cart Track ME 9429A Mass Hanger and Mass Set ME 9348 500 gram bar mass Ohaus Triple Beam Balance SE 8707 or similar Super Pulley ME 9450 Physics String SE 8050 Purpose The purpose is to verify Newton s Second Law F ma Theory Newton s Second Law F ma is a description of the relationship between F the net force acting on the object of mass m and a the resulting acceleration of the object For a cart of mass m on a horizontal track with a string attached over a pulley to a mass m see Figure 2 1 the net force F on the entire system cart and hanging mass is the weight of hanging mass F mg assuming that friction is negligible According to Newton s Second Law this net force should be equal to ma where m is the total mass that is being accelerated which in this case is m m This experiment will check to see if m g is equal to m m a Procedure 1 Level the track by setting the cart on the track to see which way it rolls Adjust the leveling screw at the end of the track to raise or lower that end until the cart placed at rest on the track will not move toward either end 2 Usethe balance to find the mass of the Dynamics Cart and record the ma
24. imer s internal microcontroller also eliminates the problem of incorrect readings due to multiple passes through the same photogate by understanding the type of measurement selected and ignoring multiple passes The Smart Timer has many different options for timing and calculating values based on inputs from a variety of sensors The graphics on the keypad aid in the selection of the appropriate timing mode Options include One or Two Gates Fence and Pendulum modes These modes allow you to measure the speed of an object as it passes through the photogate or between two photogates or to measure the period of a pendulum The stopwatch mode lets you use the timer as an electronic stopwatch The Smart Timer can measure speed and acceleration for both linear and rotational motion experiments Alternatively the time can be measured directly and the speed and acceleration can then be calculated by the student The speed and acceleration measurement features can be enabled or disabled using a switch inside the Smart Timer Use With Photogates The Smart Timer is optimized for use with PASCO s ME 9204B Accessory Photogate available separately These narrow beam infrared photogates plug directly into the Smart Timer and are used to provide the timing signals An LED in one arm of the photogate emits a narrow infrared beam As long as the beam strikes the detector in the opposite arm of the photogate the signal to the timer indicates that the
25. llisions Theory When two carts collide with each other the total momentum p mv of both carts is conserved regardless of the type of collision An elastic collision is one in which the two carts bounce off of each other with no loss of kinetic energy accomplished in this experiment through the use of the carts magnetic bumpers A completely inelastic collision is one in which the two carts hit and stick to each other accomplished in this experiment using the Velcro patches on one end of each cart Procedure PART A Inelastic Collisions l Levelthe track by setting a cart on the track to see which way it rolls Adjust the leveling screw at the end of the track to raise or lower that end until a cart placed at rest on the track will not move 2 Puta Picket Fence into the slots in the top of each cart and place the Collision Carts so the Velcro patches face each other Position the two photogates just far enough apart so the collision can take place between the photogates Adjust the height of the photogate so the 1 cm fence will block the photogate beams Connect the photogates to the Smart Timer see Figure 3 1 to channel 1 to channel 2 A Smart of the Smart Adjustable 1 cm flag Timer Photogate 2 1 cm flag End Stop Pa leveling photogate brackets Figure 3 1 Experiment setup for Conservation of Momentum experiments PASC Ci NG scientific Smart Timer 012 06734A 3 Set up the Smart Tim
26. mber represents the input jack and the following two numbers indicate the initial speed xx x and final speed yy y respectively 17 Cloro 7 scientific Table 1 Summary of Smart Timer Modes Type Speed Modes One Gate m A One Gate au Fence Fence Dan a nz Two Gates 2e Two Gates 0000 3 3 Pendulum ope Pendulum 00000 Stopwatch Em a 5 8 a a Stop Watch One NA One Gate cms BOB Collision cm s A Collision cm s Pulley Pulley rad s Pulley rev s N Pulley rev s 000000 Key Sequence Timing Diagram kt a LI Input 1 or Input tio gt t gt m PLU LU UJ LI LJ Input 1 or Input 2 k t gt mE D Input 1 Input2 k t pogi Input 1 or Input 2 Start Stop Start Stop Manual timing of events k ta A Input 1 or Input 2 kt al kts le t4 gt I CUTU IU Input1 Input 1 Input 2 le tal PU Input 1 or Input 2 le tl Fi Input 1 or Input 2 Calculation Algorithm k t Input 1 or Input 2 Automatic timing of events Speed 1cm t le ty I Speed 1cm th Input 2 Speed 2 pi rad rev 0 1rev t Speed 0 1rev t o E o m m 0 lt One Gate Linear Pulley Angular Pulley Two Gates 30 seconds 60 seconds 5 minutes Manual One Gate The key sequences shown are valid in the initial or power on situation only kti ole te a gapa Input 1 or Inp
27. mmediately is counted as an unblock and the timer alignment of the laser with the Laser Switch use the Test Gates mode will display 0 0001 seconds regardless of the length of time the first photogate is blocked 3 You cannot start the timing with the Start Stop key and end it with a photogate block or vice versa 4 If a photogate is plugged in and blocked when you try to use the Start Stop key as a stopwatch the Smart Timer will be timing the photogate and waiting for the photogate to become unblocked So when you push the Start Stop key the asterisk disappears and when you push the Start Stop key again the asterisk reappears No time is displayed until the photogate is unblocked Speed Modes One Gate In this mode a cm flag passes through the photogate The Smart Timer measures the time and calculates the average speed in cm s Collision In this mode either one or two carts and one or two photogates can be used for a collision experiment Once Start Stop is pressed the Smart Timer waits for the first collision and begins timing The Smart Timer stops timing when two carts have passed through their respective photogates twice Timing can always be stopped manually by pressing Start Stop and the Smart Timer will display speed s based on the information it has you will need to press Start Stop for single cart collisions The display will present the results in the following format 1 xX x yy y 2 XX X yy y The first nu
28. n typical use Experiments Four copy ready experiments and 9 additional suggested experiments are included in this manual showing a variety of ways to use the Smart Timer The equipment requirements vary for different experiments For many of the experiments you will need a Dynamics Track and Dynamics Carts Some experiments also require two ME 9204B Accessory Photogates or the ME 9387 Smart Pulley Check the equipment requirements listed at the beginning of each experiment 012 06734A Smart Timer Equipment Included Smart Timer Smart Timer Picket Fences 2 9 VDC adapter liquid crystal display mode illustrations g d een SMART TIMER connector for 9VDC adapter side panel M araia o Puloy Puley ads sj battery compartment on off switch bottom panel side panel 3 2 HECTEREERT EN input channel 2 touchpad keys input channel 1 9 VDC adapter 5 cm fence 1 cm flag 1 cm fence E 3 3 E qu n 3 EJ E Ss z s a 4 2 Ea ASE a a l H i i EZ 1 m i i i Figure 1 Smart Timer Picket Fences Included equipment Smart Timer 012 06734A Operating the Smart Timer 1 Plug the Y4 inch phone plug from the photogate into the Smart Timer s input channel 1 or 2 see Figure 2 For all experiments using a single photogate or pulley either of the two available jacks may be used inter
29. ngle timer Some of the experiments in this manual require the use of a Smart Timer with two Accessory Photogates 12 12 elo 01 2 06734A Smart Timer Time of Flight Accessory ME 6810 The Timer of Flight Accessory facilitates the accurate measurement of the flight time of a ball launched by a PASCO projectile launcher See page 33 Time of Flight and Initial Velocity and Figure 9 1 for details of the setup Free Fall Adapter ME 9207B The Free Fall Adapter facilitates easy and accurate measurements of the acceleration of gravity It comes with everything you need including two steel balls of different size and mass a release mechanism and a receptor pad The release mechanism and the receptor pad automatically trigger the Smart Timer so you get more accurate measurements of the free fall time of the steel ball See page 34 Determining the acceleration due to gravity g with the Free Fall Adapter and Figure 10 1 for details of the setup Laser Switch ME 9259A This highly collimated photodetector is identical to a photogate except that a laser available separately is used as the light source With the Laser Switch the motion of objects that are too big to fit through a standard photogate can be measured Thus you can measure the period of a bowling ball pendulum or the velocity of a car for example G M Tube Power Supply SN 7927 The G M Tube Power Supply is a Geiger Muller Probe that senses beta gamma and al
30. onservation of Energy Experiment 8 Use a Photogate and the Smart Timer instead of a computer and IDS Timer software and set the experiment up as directed in the experiment Set up the Smart Timer to measure Speed One Gate To measure the velocity of the cart activate the Smart Timer and before releasing the plunger of the Dynamics Cart 012 06734A Smart Timer Note The following experiment is in copy ready form in the manuals for the Mini Launcher manual number 012 05479 and the Ballistic Pendulum Projectile Launcher manual number 012 05375 Projectile Motion Using B a Timer channe Photogates Experiment 2 Pa Use the Smart Timer instead of a computer and IDS Timer Photogates software and set the experiment To Smart Timer up as directed in the experiment channel 1 Plug the photogates into the Smart Timer as shown in Figure 8 1 and set up the Smart Timer to measure Time Two Gates Photogate Mounting Bracket Press l to activate the Smart Timer and fire the launcher Calculate the initial velocity using the time required for the ball to pass through the photogates FH ME 6825 Mini Launcher or ME 6800 Projectile Launcher Figure 8 1 Setup for the Projectile Motion Using Photogates Experiment Note The following experiment is in copy ready form in the manual for the Time of Flight Accessory manual number 012 05088 Time of Flight and Initial Velocity Experiment 1
31. or brief periods Strong ultraviolet light can damage the Smart Timer display Remove the batteries prior to storage for more than one month Batteries can leak and damage the internal circuitry especially if the batteries are old For best results use alkaline batteries Rechargeable NiCad batteries may be used but the operating time between charges is much shorter than the lifetime of alkaline batteries Specifications Resolution The basic timing resolution of the Smart Timer is 100 microseconds in all modes except Stopwatch which is 10 ms Calculated Values Calculated values are displayed to one or two decimal places with typical accuracy being 1 in the least significant digit For extremely high speeds such as might be generated by hand spinning a Super Pulley accuracy is degraded for calculated parameters because of the very short timing intervals involved Maximum Output Power The Smart Timer allows many different accessories to be used as inputs The total 5 volt load both inputs added together that can be accommodated is 180 mA maximum Accessory Options The following PASCO accessories are available to help extend the utility of the Smart Timer See the current PASCO catalog for more information Accessory Photogate ME 9204B The stereo phone plug of the Accessory Photogate plugs into either of the phone jacks on the side of the Smart Timer giving you the option of two identical photogates operating from a si
32. pha radiation See page 34 Counting radiation with the G M Tube Power Supply and Figure 11 1 for details of the setup PASCOR 13 Smart Timer 012 06734A 14 012 06734A Smart Timer Experiment One Acceleration Due to Gravity EQUIPMENT AND MATERIALS REQUIRED Smart Timer ME 8930 Photogate ME 9498A Purpose Smart Timer Picket Fence The purpose is to determine the acceleration due to the Earth s gravity Theory The accepted value for the acceleration due to gravity on the Earth s surface is 9 8 m s With the Smart Timer the acceleration due to Earth s gravity can be quickly determined experimentally The acceleration may be calculated from measurements of distance and time or it can be measured directly To calculate the acceleration from time measurements the following formula must be used Av V22 V1 8T Ar Wht where v 5cm and v 5cm 1 1 1 Note that At is not t but is 1 2 t see Figure 1 1 NS 19144 Y t5 ti zl5t l5t l 5t At 1 ty Figure 1 1 Explanation of why Yat is used in the formula for calcu lating g Procedure PART A Determining the acceleration from time and distance measurements 1 Mount the photogate on a stand or hold the Photogate steady so it is parallel to the floor as shown in Figure 1 2 The 5 cm fence should block the photogate beam Picket Fence must be dropped at a 90 angle Photogate Smart Time
33. r Picket Fence To Smart Timer channel 1 or 2 Figure 1 2 Experiment setup 15 Smart Timer 012 06734A 2 Insert the plug of the photogate into channel 1 or 2 of the Smart Timer and set up the Smart Timer to measure Time Fence 3 Hold the Smart Timer Picket Fence in a position so it will drop vertically through the photogate and so the 5 cm fence will block the photogate beam as the fence drops through the photogate Note Three conditions must be met for greatest accuracy 1 The Picket Fence must be dropped at a 90 angle to the photogate beam in such a way that it does not rotate on the way down One method to improve the drop is to hold the edge of the Picket Fence with a clothspin or binder clip and drop the fence by squeezing the clothespin or clip 2 The Picket Fence must be dropped so the 5 cm marks cut the photogate beam 3 The Picket Fence must pass close to the LED that emits the photogate beam 4 Press El and drop the fence 5 Record t and t and calculate the acceleration in meters second PART B Determining the acceleration directly 1 Repeat steps 1 4 in Part A with the following modification Set the Smart Timer to measure Acceleration One Gate Repeat several times and calculate the average acceleration g Questions 1 How do the two methods for determining the acceleration on a body due to Earth s gravity compare 2 How do the experimental measurements compare to accepted valu
34. requirement The photogate must be blocked twice within two seconds to obtain a valid reading translating to a minimum speed of 0 31 rad s Pulley rev s Besides displaying in different units this mode uses the display differently than in the radians second measurement The display provides a real time measurement of the speed of the pulley by updating once per second Once a speed is displayed press the Start Stop key to freeze the display The Smart Timer indicates that the measurement is in the first column Press Start Stop to erase the eq eq frozen by displaying a and start eq collecting new measurements Any time the first column is blank or has a displayed the type of measurement being done can be changed by pressing the Select Measurement or Select Mode keys To move to a different measurement press Start Stop again Like the radians second measurement there is a two second maximum time for two photogate blocks translating to a minimum speed of 0 05 rev s Also note that accuracy decreases rapidly as pulley speeds increase above 600 rpm At 600 rpm accuracy is 1 Acceleration Modes One Gate The Smart Timer uses the time measurement between two equally spaced 5 cm block unblock block sequences to calculate average acceleration In activities using the Smart Timer Picket Fence the Picket Fence must be positioned so that the photogate blocks only the 3 bar segment 5cm fence of the Picket Fence Note th
35. s at one end with the 1M in front of 3M Give 3M a slightly greater velocity than 1M so the carts collide between the photogates Table 3 1 Data Note Do each experiment at least 3 times 20 PA e 012 06734A Smart Timer Analysis I For each of the cases calculate the momentum of each cart before the collision Record the results in Table 3 2 2 For each of the cases calculate the total momentum of both carts before the collision Record the results in Table 3 2 3 For each of the cases calculate the total momentum of both carts after the collision Record the results in Table 3 2 4 For each of the cases calculate the percent difference between the total momentum of the carts before and after the collision and record in the table Questions Table 3 2 Results P P of TOTAL TOTAL Trial 1 man 1 When two carts moving toward each other have the same mass and the same speed they stop when they collide and stick together What happens to each cart s momentum Is momentum conserved Explain 2 Kinetic energy is not conserved in inelastic collisions For one of the collisions calculate the percentage of the kinetic energy that is lost in the collision Where does this energy go PASC Ce 21 Smart Timer 012 06734A Part B Elastic Collisions Set up the carts so the magnetic ends face each other so the carts will repel each other when they collide Record the data in Tables 3 3 and 3 4
36. sofRing Accounting for Friction 1 Setup the Smart Timer to measure Speed Pulley rev s 2 Tie several paper clips onto the string that hangs over the Smart Pulley 3 Start the disk spinning slowly 4 Adjust the hanging mass number of paper clips until the speed remains constant 5 Record this friction mass in Table 4 2 6 Repeat for each setup below ring and disk combined disk alone and disk vertical Measurements for Determining the Rotational Inertia Experimentally 1 2 Set up the Smart Timer to measure Acceleration Linear Pulley cm s Find the acceleration of the ring and disk using a hanging mass of about 50 g Wind the thread up and let the mass fall Record the acceleration press EJ when the mass has fallen about 1 3 of the total fall distance to minimize the effect of friction Repeat at PASC 27 Smart Timer 012 06734A 28 least three times and record the average values for weight of the hanging mass and acceleration in Table 4 2 Using calipers measure the diameter of the pulley about which the thread is wrapped and calculate the radius Since in step 2 the disk is rotating as well as the ring it is necessary to determine the acceleration and the rotational inertia of the disk by itself This rotational inertia can be subtracted from the total leaving only the rotational inertia of the ring To do this take the ring off the rotational apparatus and repeat step 2 using a hanging mass
37. ss in Table 2 1 3 Attach the Super Pulley to the end of the track as shown in Figure 2 1 4 Connect the Photogate to the Smart Timer and adjust the Photogate so that when the pulley turns the spokes of the pulley will block the photogate beam to Smart Timer ff Dynamics Cart PA Photogate Photogate Bracket Adjustable End Stop IDS Track Figure 2 1 Mass Hanger and Mass Experiment setup to determine the acceleration of the masses PASCO 17 Smart Timer 012 06734A 5 Place the Dynamics Cart on the track attach a string to the hole in the end of the cart and tie a mass hanger on the other end of the string The string must be just long enough so the cart hits the end stop before the mass hanger reaches the floor 6 Pullthe cart back until the mass hanger reaches the pulley Make a test run to determine how much mass is required on the mass hanger so that the cart takes about 2 seconds to complete the run Record the hanging mass in Table 2 1 7 Set up the Smart Timer to record Acceleration Linear Pulley Note Use masses of between 50 and 100 g and be sure that the runs are not longer than 2 seconds 8 Pull the cart back until the mass hanger reaches the pulley Release the cart from rest and activate the Smart Timer once the car has started moving The timing will begin when the photogate beam is first blocked Repeat this measurement 3 times with the same masses Record all the values in T
38. te being blocked and a depressed line corresponds to the photogate being unblocked The calculation modes assume the use of a fence of fixed width 1 cm or 5 cm or a pulley having a diameter groove to groove of 4 8 cm and 10 spokes such as the Super Pulley or Smart Pulley LOCK Switch The internal LOCK switch provides a way to temporarily lock out speed and acceleration modes To access the LOCK switch turn the power off and remove the bottom half of the Smart Timer case as if you were going to replace the batteries Look along the lower edge of the printed circuit board and ee Unlock LOCK switch note the LOCK switch button at the edge Figure 3 The circuit Cock board also has the words LOCK and UNLOCK printed along the same edge Moving the switch to the LOCK position Figure 3 will cause the display to read MODE UNAVAILABLE Location of the LOCK switch on the circuit whenever speed or acceleration modes are selected board 11 FAS C CN scientific Smart Timer 012 06734A Caring for the Smart Timer e Do not use a pointed object such as a pen to press the keypad buttons Wrap the Smart Timer separately when transporting it with other items The transparent covering over the keypad can be creased by a fingernail or other sharp object Clean the keypad with a soft cloth and mild detergent avoiding hard rubbing of the transparent window Do not leave the Smart Timer exposed to direct sunlight except f
39. ustomer 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 Equipment Return Should the product have 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 gt 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 D The packing carton must be strong enough for the item shipped Make certain there are at least two inches of packing material between any point on the apparatus and the inside walls of the carton 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 10101 Foothills Blvd Roseville CA 95747 7100 Phone 916 786 3800 FAX 916 786 3292 email techsupp pasco com web www pasco com PASC Ce scientifi
40. ut 2 k t1 gt lt t2 Pipas E Input 1 or Input 2 k t gt k t2 pistes e eS oS DES Input 1 or Input 2 t P l FT Accel 2 5cm t1 5cm t2 t1 t2 Accel 2 0 4rev 15cm t 0 4rev 15cm t2 t4 t2 Accel 2 0 4rev 2 pi 1 t4 1 to t4 t2 dT t4 dT gt tz to dT ty tz to 2 ty 2 t2 t3 ty 2 JU v4 1cm dT4 va 1cm dT dV v vy Input 1 Input 2 a dV dT lt t 30s _ gt 1 E n XN el Count n Input 1 or Input 2 DEF en 1 2 n A As Count n Input 1 or Input 2 lt t 3005 __ 1 7 un ada n ea SEM Count n Input 1 or Input 2 Mai ma 1 2 5 1 aan n TETE Count n Input 1 and or Input 2 Key Photogate Blocked Photogate Unblocked Note The length of the line is not related to the length of the time interval Smart Timer 012 06734A Pulley rad s The Smart Timer will measure the speed of a pulley passing through a photogate in units of radians second One measurement will be taken each time the Start Stop switch is pressed The Smart Timer cannot differentiate between clockwise and counterclockwise directions Note that as in many other modes if a shows in the first character position of the second line the Smart Timer is actively waiting for an external timing event to occur If the is not showing the Timer measurement mode may be changed This mode has a minimum speed
41. ut channel 1 and the second photogate into input channel 2 Pendulum In Pendulum mode the timer measures the period of one complete oscillation Timing begins as the pendulum first cuts through the beam The timer ignores the next interruption which corresponds to the pendulum swinging back in the opposite direction Timing stops at the beginning of the third interruption as the pendulum completes one full oscillation Press the Start Stop key again to begin a new timing cycle Stopwatch The Manual mode is actually a dual use function It provides a means of manually timing events like a using a Stopwatch by pressing the Start Stop key It also allows timing of events using the ME 9207B Free Fall Adapter and the ME 9259A Laser Switch which function via a block unblock sequence Using the Stopwatch Enter Stopwatch mode and press the Start Stop key The Smart Timer will beep and a will appear on the second line of the LCD Press the Start Stop key again to start the timer Press the Start Stop key to stop timing and display the elapsed time Press the Start Stop key again The old result is gt Note The picket fence supplied with the Smart Timer is designed to increase timing accuracy when used with photogates The fence has three sections the 1 cm flag the 5 cm fence and the 1 cm fence one of these must be aligned with the photogate light path before the experiment can proceed 012 06734A Smart Timer
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