VERNIER SOFTWARE PHYSICS WITH THE TI CBL AND TI-85 I. OVERVIEW II. MEMORY REQUIREMENTS III. GROUP FILES IV. SENDING GROUP FILES - MAC V. SENDING GROUP FILES - WINDOWS VI. UNGROUPING FILES VII. GENERAL DESCRIPTION OF THE PROGRAMS VIII. DATA STORAGE IX. PERFORMING EXPERIMENTS WITH THE MICROPHONE X. OVERVIEW OF EACH PROGRAM XI. POSSIBLE ACTIVITIES XII. PROGRAM DESIGN NOTES I. OVERVIEW This document describes the use of a group of programs that help you perform experiments with a TI-85 calculator and the TI Calculator-Based Laboratory (CBL) System with Vernier sensors commonly used in physics. With this program you will be able to use a motion detector, force sensors, accelerometers, microphones, pressure sensors, temperature probes, light sensors, voltage leads, and current probes. Data collection modes can be used to 1) monitor CBL channels, 2) collect data as a function of time, 3) collect data with a manually-entered independent variable, and 4) collect data using the trigger button on the CBL. Time graphs generated in real time are possible but this option only works when one or more of the same probe is are active. If the active probe is the Motion Detector, a live graph of distance vs. time is drawn and neither velocity nor acceleration data will be calculated. When more than one different sensors are active or when you want distance, velocity and acceleration from the Motion Detector, the time graphs will be displayed after the data is collected. When the Motion Detector is used in conjunction with the other sensors, only two of these probes can be active. This occurs because the program was designed to match the TI-82 version and that calculator is limited to six lists, four lists being used for motion data. One of the features of the TI-85 is the ability to model data with eight different regression models. In working with real data, it is helpful to select a region of data with which to work. Since the TI-85 applies the regression models to the entire list, the calculated fit may be affected by unwanted data. With this program it is possible to select a region of the graph and automatically delete unwanted data outside the region of interest for each of the data lists. III. MEMORY REQUIREMENTS It is possible that you may run into "memory error" problems when using this set of programs. These errors may occur for two reasons. 1) This entire set of programs will require a considerable amount of the available memory on the TI-85. 2) If you use a motion detector in combination with other probes, large amounts of data may be collected. If you run into memory errors, you may have to collect less data or you may have to free up calculator memory by deleting lists, matrices, pictures and/or programs. If there are certain data collection modes you are not using, e.g. trigger, you can delete programs associated with these modes—PHZTRIGG in this example. (You will find a description of each program later in this document.) You may also want to consider deleting the PHZMICRO program if you are not going to use the microphone. Refer to the calculator manual for help with deleting files. III. GROUP FILES The PHYSCS85.85g file is nine programs that have been grouped together. (Groups of files for the TI-85 always end in the "85g" while program files have the extensions "85p". The extensions on the filenames appear only on the computer and do not appear when you see the program names on the calculator.) The easiest method of loading all nine programs on to your calculator is to transfer the PHYSCS85.85g group file. IV. SENDING GROUP FILES - MACINTOSH 1) Connect the TI-GRAPH LINK cable to the modem port of the Macintosh computer and to the port on the bottom edge of the TI-85. 2) On the TI-85 calculator, use LINK, then select Receive (“Waiting...” appears on the TI-85 screen. 3) Using the TI-GRAPH LINK software on your computer, choose Group from the Send menu. 4) Open the PHYSCS85.85g file from the TI-85 folder in your Vernier CBL Data Collection disk (or on your computer hard drive). 5) Click on the Send button. The nine programs are now loaded into your TI-85 calculator. V. SENDING GROUP FILES - WINDOWS 1) Connect the TI-GRAPH LINK cable to the serial port of your computer and to the port on the bottom edge of the TI-85. 2) On the TI-85 calculator, use LINK, then select Receive (“Waiting...” appears on the TI-85 screen. 3) Using the TI-GRAPH LINK software on your computer, choose Send from the Link menu. 4) Select PHYSCS85.85g from the TI-85 folder in your Vernier CBL Data Collection disk (or on your computer hard drive). 5) Click on the OK button. The nine programs are now loaded into your TI-85 calculator. VI. UNGROUPING FILES You may prefer to "ungroup" the PHYSCS85.85g file for archiving on a hard drive. Before you do that, it would be best to create a folder or subdirectory on your hard drive for the group file. The programs can then be stored in a common area on your hard drive after being ungrouped. The files can be ungrouped by choosing the Ungroup Files option in the TI-GRAPH LINK program. Ungrouping the file will make the following nine programs available: PHYSICS.85p, PHZCALIB.85p, PHZCALS.85p, PHZGRAPH.85p, PHZMICRO.85p, PHZMONIT.85p, PHZOPTIO.85p, PHZTIMEG.85p, and PHZTRIGG.85p. The TI-GRAPH LINK will also allow you to download all nine programs from the computer to the calculator. VII. GENERAL DESCRIPTION OF THE PROGRAMS These nine programs function together to provide a wide range of options as you create and run experiments. After all nine programs have been loaded, run the PHYSICS.85p program. (Remember, the name of the program will appear as "PHYSICS" on the calculator). The PHYSICS.85p program uses a series of menus allowing you to set up different types of experiments with a combination of probes. The following general description applies to the use of these programs on the TI-85 calculator. For specific help in executing programs on the calculator, refer to the manual. To begin, run the PHYSICS program. After an introductory screen, the following MAIN MENU will appear: ***MAIN MENU*** SETUP=SET UP PROBES COLL =COLLECT DATA VIEW =VIEW GRAPH RETRI=RETRIEVE DATA MORE =MORE The CBL provides access to three analog channels, channels 1 - 3, for devices such as force sensors, accelerometers, and temperature probes. One sonic channel is available for an ultrasonic motion detector. When you choose the first option, SET UP PROBES, from the above menu, you will be able to 1) enter the number of active probes, 2) choose a probe, 3) enter the CBL channel number for any analog device, and 4) choose the method of calibrating analog probes. If you are using a Motion Detector, you will not be prompted for a channel number since the Motion Detector will only work in the sonic channel. As you connect analog probes to the CBL, connect each to the lowest available channel. (Note: this program was designed to match a similar program for the TI-82. Since the TI-82 is limited to six lists, this program will limit the number of analog devices to two when you are using the Motion Detector.) After you select this option and enter the number of probes, the following menu will appear: SELECT PROBE MOTIO=MOTION FORCE=FORCE ACCEL=ACCELEROMETER MICRO=MICROPHONE MORE =MORE PROBES The first option represent the Vernier Motion Detector. The second option, FORCE, will bring up a menu from which you can choose the Vernier Student Force Sensor or the PASCO Force Sensor. The third option, ACCEL, brings up a menu from which you can choose the Low-g or 25-g Accelerometer. The fourth option, MICRO, works for the CBL, MPLI, or ULI microphone. (When you select this option, you will be sent to a subprogram to collect data. This program is explained later.) The last option produces this list of probes: SELECT PROBE PRESS=PRESSURE TEMPE=TEMPERATURE LIGHT=LIGHT MAGNE=MAGNETIC FIELD MORE =MORE PROBES The PRESS option represents the Pressure Sensor. The second option, TEMPE, is used for the TI Temperature Probe or the Vernier Direct- Connect Temperature probe. The LIGHT option can be used for either the TI Light Probe or the Vernier Light Sensor. The fourth option, MAGNE, represents the Magnetic Field Sensor. The last option produces this list of probes: VOLTS=VOLTAGE CVCUR=C-V CURRENT CVVOL=C-V VOLTAGE THERM=THERMOCOUPLE MORE =MORE PROBES The VOLTS option is used for either the TI Voltage probe or the Vernier Voltage Leads. The CVCUR option is used with the Current and Voltage System Current Probe while the CVVOL option represents the Current and Voltage System Voltage Probe. The THERM option is used with the Thermocouple. The MORE option produces the last list of probes: SELECT PROBE VERN =VERN STD TEMP VERN =VERN QIK TEMP CUSTO=CUSTOM RETUR=RETURN The first option refers to the Vernier Standard Temperature Probe while the second option refers to the Vernier Quick-Response Temperature Probe. The CUSTO option can be used for a custom probe. The RETURN option returns you to the first list of probes. The above lists will appear up to three times depending upon the number of probes you entered. After you select an analog probe, you will be asked to enter the channel number for that probe. After you enter the channel number, you will be presented with the following CALIBRATION menu: **CALIBRATION** USE S=USE STORED PERFO=PERFORM NEW MANUA=MANUAL ENTRY The first option, USE STORED, in the above menu allows you to load standard slope and intercept values for Vernier probes. These are "generic" slope and intercept values determined by Vernier Software. The values will provide reasonably accurate measurements but individual probes differ and you may obtain better results by performing a new calibration. (The PHZCALS.85p program contains the Vernier standard slope and intercept values. It is possible to edit this program and enter the slope and intercept values for your probes.) If you choose to perform a new calibration, it is helpful to understand the operation of Vernier probes other than the Motion Detector. During their operation, the probes produce a voltage that is linearly dependent upon a physical quantity. For example, the Student Force Sensor produces a voltage that varies linearly with the applied force. During the calibration process, the computer establishes the linear relationship between voltage and force. Choosing the PERFORM NEW option will allow you to perform a two-point calibration for the probe that was just set up. The following paragraph describes the calibration process for a Student Force Sensor. The same general procedure can apply to the any analog sensor. After you choose the PERFORM NEW option from the above menu, remove all forces from the Force Sensor. Monitor the CBL display for the voltage produced by the probe. When the voltage stabilizes, press the [TRIGGER] button on the CBL. You are then prompted to enter the reference value, 0 Newtons in this case. Apply a known force to the sensor as a second reference. The easiest method is to hang a labeled mass from the beam end of the sensor. For example, a 200-g mass weighs 1.96 N. The voltage is again monitored and the [TRIGGER] button is pressed when the voltage stabilizes. Enter the second reference value. A slope and intercept for the linear calibration curve are then be displayed on the calculator and loaded into the CBL. You may want to record these values for future reference (see the section below). This process can be repeated for other Vernier probes. For further help with other sensors and probes refer to the information sheet for those devices. The MANUAL ENTRY option in the Calibrate Menu is an option that may save you time in setting up future experiments especially if you have performed calibrations for your probes. Probes such as the Force Sensor hold their calibration for long time periods. If you know the slope and intercept values determined in the above process, you can manually enter these values with this option. After the channels and probes are set up, you will return to the MAIN MENU. From the MAIN MENU you can set up an experiment by choosing the second option, COLLECT DATA. The following menu provides you with a choice of data-collection modes: DATA COLLECTION MONIT=MONITOR INPUT TIME =TIME GRAPH PRMPT=TRIGGER/PROMPT TRIGG=TRIGGER RETUR=RETURN The MONITOR INPUT option is used to monitor the active channels with the calculator. The purpose of this option is to view data at 1.0 second intervals. No data is stored. For all probe combinations, each active channel will be displayed on the calculator. When done monitoring the channels, press the [+] key on the calculator to quit. The TIME GRAPH option from the DATA COLLECTION menu is used to collect data as a function of time. A screen will prompt you to enter the time between samples which is entered in seconds. The sample time can be in the following range of values: 0.000164 to 0.2 seconds or 0.25 to 16000 seconds. However, the minimum sample time depends upon the number and types of active probes and the data collection mode. If you plan to use a live display where a graph is shown during data collection and you only have one probe, the minimum sample time is 0.1 s regardless of the type of probe. (If you enter a time less than 0.1 seconds, you will not get a live display.) If you enter a value between 0.1 s and 0.2 s and you use a live display, the CBL will collect data at 0.1 s. If you have two similar probes, the minimum sample time for a live display is 1 s. If you have three similar probes, the minimum sample time for a live display is 1.25 s. If you are going to collect data without a live display, the minimum sample time for one analog probe is 0.000164 s. For two analog probes the minimum time is 0.000264 and for three probes it is 0.000364 s. The minimum sample time for the Motion Detector with a non-live display is 0.008 s. (The minimum sample time will increase by 0.0006 s if you use the manual trigger option, a feature available in the OPTIONS menu.) If you enter a value less than the minimum sample time, the calculator will use the minimum sample time allowed for your setup. To automatically collect data at the minimum sample time, enter 0 as the sample time. After the sample time is entered, you will be prompted to enter the number of data points. The maximum number being 512. (As mentioned earlier the amount of available memory may limit the number of data points you can collect.) Under some conditions the following menu will appear allowing you to choose between live and non-live displays: COLLECTION MODE NON-L=NON-LIVE DISPL LIVE =LIVE DISPLAY This menu will appear under these conditions: 1) only one type of probe is active, 2) triggering is not being used to start data collection, 3) the sample time is greater than or equal to the minimum value for a live display, and 4) the sample time is less than 270 s (4.5 minutes). The NON-LIVE DISPL option will collect data without displaying a graph during data collection. This option provides the greatest flexibility in designing experiments by permitting combinations of probes, triggering, and a wider range of sample times. (If you did not see the above menu the data will be collected without a live display.) If the Motion Detector is active, only two analog channels can be active. If you are only using analog channels, you will see graphs of each channel when data collection is complete. If the Motion Detector is the only active channel, then you will be able to choose from three graphs- distance vs. time, velocity vs. time, and acceleration vs. time. If you are using the Motion Detector and analog probes, you will be able to choose between the analog channels and motion data. The LIVE DISPLAY option produces a "real-time" graph during data collection. However, this option will only work with probes of the same type and if the sample time is less than or equal to 270 seconds. Please note that the time base during data collection with a live display is only approximate. To record an accurate time base, use the Non-Live Display option. If the experiment is longer than 270 seconds (4.5 minutes) and non-live or you are using a manual trigger, the experiment is considered to be a long-term experiment since the calculator will automatically power down. A message will direct you to use the RETRIEVE DATA option from the MAIN MENU. Select this option after the data collection is complete when the CBL display shows "DONE". After the option is chosen, the data will be retrieved from the CBL and the graph or graphs will be displayed. Each time you view a graph, you will be able to read off the coordinates of each data point. The coordinates of the first point will be displayed on the bottom of the screen. To view other points use the left and right arrow buttons on the calculator to move across the screen. The TRIGGER/PROMPT option in the DATA COLLECTION menu is used to perform experiments in which the independent variable is entered from the calculator keyboard while the dependent variable is measured with the CBL probe or probes. For example, you could use a Light Sensor to measure the light intensity as the distance from the source changes. When the [TRIGGER] button on the CBL is pressed, the CBL measures the light intensity and you will be prompted to enter the distance from the source. After you select this option, a screen will appear prompting you to press the CBL [TRIGGER] button when you are ready to take a sample. You will then be prompted to enter the independent variable. The following menu then appears: DATA COLLECTION MORE =MORE DATA STOP =STOP AND GRAPH PAUSE=PAUSE If you select MORE DATA, the CBL will be set up to make another reading. If you select STOP AND GRAPH, data collection will stop and a graph will be displayed. If you select PAUSE, the calculator will be put in a pause mode. When you are ready to collect more data, press [ENTER] on the calculator and follow the on-screen instructions. If the calculator has powered down due to the APD, turn on the calculator, then press the [ENTER] key. The TRIGGER option in the DATA COLLECTION menu is used to manually sample each active channel when the [TRIGGER] button on the CBL is pressed. (In this data-collection mode, you do not enter an independent variable as done in the TRIGGER/PROMPT mode.) Each time you press the [TRIGGER] button, you will get the following screen: TRIGGER CONTI=CONTINUE STOP =STOP PAUSE=PAUSE If you select CONTINUE, the CBL will be set up to make another reading. If you select STOP, data collection will stop and you will return to the MAIN MENU unless there are two active probes in which case a graph will be drawn. If you select PAUSE, the calculator will be put in a pause mode. When you are ready to collect more data, press [ENTER] on the calculator and follow the on-screen instructions. If the calculator has powered down due to the APD, turn on the calculator, then press the [ENTER] key. During the data collection process in the TRIGGER/PROMPT and TRIGGER modes you can monitor each active channel by pressing and holding the [CH VIEW] button on the CBL. Repeated pressing of this button will cycle you through the active channels. The VIEW GRAPH optin on the MAIN MENU allows you to review previously set up graphs. As you view each graph, you will be able to use the left and right arrow buttons on the calculator to view the coordinates of each point. These graphs use the "ZoomStat" option to provide automatic scaling of axes. You may prefer to quit the program to set your own scaling. The RETRIEVE DATA option on the MAIN MENU is used after data is collected during a long-term experiment. Before you select this option, be sure the CBL is done collecting data. (The word "DONE" should appear in the CBL display.) The MORE option in the MAIN MENU brings up this menu: OPTIO=OPTIONS QUIT =QUIT RETUR=RETURN OPTIONS will bring up this menu: PHYSICS OPTIONS SELEC=SELECT REGION INTEG=INTEGRATE MANUA=MANUAL TRIGGER TRIGG=TRIGGERING RETURN The first option SELECT REGION is used to select a portion of data. This feature is helpful in deleting extraneous data thereby making it easier to model data. After this option is selected, a menu will appear asking you which graph you wish to examine. This graph will then be displayed so that you may select a region of data. Use the arrow keys to move the cursor and select the lower limit of the region and press [ENTER]. A horizontal line will be drawn on the graph. Now move the cursor to select the upper limit and press [ENTER]. Data above and below these limits will deleted from ALL lists. The second option, INTEGRATE, is used to integrate a section of the graph. After selecting this option, choose a graph from the list displayed on the screen that follows. Use the arrow keys to move the cursor and select the lower limit of the region and press [ENTER]. A horizontal line will be drawn on the graph. Now move the cursor to select the upper limit and press [ENTER]. (Note: The process uses a "snap to" function in choosing the point nearest your selection.) After the integration is performed, vertical lines will be drawn to represent the integrated area. Press [ENTER] to see the numerical results. The third option, MANUAL TRIGGER, will bring up a menu asking you if you wish to use a manual trigger. When you are performing a time graph experiment with a manual trigger, the data will not be collected until you press the [TRIGGER] button on the CBL. This is helpful when you want to collect data while the CBL is disconnected from the calculator. You can reconnect the calculator to the CBL and use the RETRIEVE DATA option to retrieve the data from the CBL, and then analyze the data on the calculator. The fourth option, TRIGGERING, will set up the CBL to begin collecting data when the signal from Channel 1 or 2 reaches a certain value. You can trigger on any analog probe except the TI temperature probe. After selecting this option, you will choose the trigger channel. Next you will choose whether the measurement is rising or falling. You will then enter the trigger value and the amount of prestore data. This amount can be an integer between 0 and 100. VIII. DATA STORAGE During data collection data is stored in the following lists: time or independent variable in l1 motion detector distance in l4 velocity in l5 acceleration in l6 analog channels channel 1 in l2 channel 2 in l3 channel 3 in l4 During the data collection process you can monitor each active channel by pressing and holding the [CH VIEW] button on the CBL. Repeated pressing of this button will cycle you through the active channels. IX. PERFORMING EXPERIMENTS WITH THE MICROPHONE When you select the Microphone from the list of probes during probe setup, a separate program will be run. The primary use of this program is to produce waveform graphs of sound pressure as a function of time. If you are using a CBL or MPLI Microphone you will be able to monitor the frequency of a sound signal. If waveform data is collected, it is possible to model the data with a trigonometric function. The program defines equation Y1 with an appropriate form. We have found that the best waveforms occur when the peak voltage from the microphone is in the range of 0.5 to 1.0 volts. If the signal is much smaller than that, the quality of the waveform decreases. If this is the case, you may need to produce a louder sound or move the source closer to the microphone. When the waveforms are displayed by this program, you can use the arrow buttons to trace the waveform and check the voltage of the signal noting the maximum or minimum y values. After choosing Microphone from the list of probes, a screen will appear reminding you to connect the microphone to Channel 1. The following screen will appear next and you will have to choose the type of microphone you are using. SELECT MICROPHN CBL =CBL ULI =ULI MPLI =MPLI The next screen provides a list of data collections modes. COLLECTION MODE WAVEF=WAVEFORM WAVEF=WAVEFORM/TRIGR FREQU=FREQUENCY RETUR=RETURN If you choose WAVEFORMS a screen will appear prompting you to hold a sound source close to the microphone. After you press the [ENTER] key on the TI-85, the CBL will quickly sample the sound source. A display of sound pressure vs. time will be displayed on the calculator and you can use the arrow keys to trace data points on the graph. After you press [ENTER] from the graph screen, you will be asked whether you want to repeat the data collection. If not, you will return to the MAIN MENU. During sampling the time is stored in list l1 and voltage which is proportional to sound level is stored in list l2. The WAVEFORM/TRIGR option also produces a waveform but this time the CBL is placed in a trigger mode. The CBL will not start to collect data until the voltage reaches 0.2 V. (Note: this mode will only work with the CBL or MPLI microphone.) Once the trigger occurs, sampling begins and a graph of sound pressure vs. time will be displayed. After you select this option, a screen will prompt you to press [ENTER] to make the CBL ready. The CBL will then wait for a trigger. After the data is collected, the graph will be displayed and you can use the arrow keys to trace the data points on the graph. Again the time is stored in l1 and sound level is stored in list l2. The FREQUENCY option will monitor a sound source held near the microphone and display its frequency in hertz. (Note: this mode will only work with the CBL or MPLI microphone.) After you select the option, you will be instructed to press the [ENTER] key to prepare the CBL to collect data. The next screen will prompt you to hold a sound source close to the microphone. When the sound intensity reaches a certain level, the CBL will be triggered and the signal will be monitored. If the sound is weak, you may have to hold the source very close to the microphone. After a short time, the frequency will be displayed on the calculator. The frequency will be stored in list l1. After you press [ENTER], you will be given the opportunity to repeat the data collection. EDITING THE TIME BETWEEN SAMPLES When waveforms are collected, this program is set up to collect data as fast as possible. The minimum sample time in this situation is 0.000165 s. You may want to change this value. This is done by editing the Sample and Trigger Command (command 3) in the PHZMICRO program. If you are collecting waveforms using the WAVEFORMS option, locate this command, {3,.000165,99,0,0,0,0,0,1,0}->l6 within the Lbl 1 section. If you are collecting waveforms using WAVEFORM/TRIGR, locate this command {3,.000165,99,2,1,.2,0,0,1,0}->l6, within Lbl 2 section. To increase the time between samples, edit the second number in these commands. For help in editing TI-85 programs, refer to the TI-85 Guidebook. X.OVERVIEW OF EACH PROGRAM The PHYSICS.85p program will call the other programs depending upon the options you choose. Each program is briefly described below. PHYSICS.85p - This is the main program that controls the set up of the probes and the experiment. Begin by running this program. PHZCALIB.85p - This calibration program provides three options allowing you to: 1) to use a default calibration, 2) perform a new calibration, and 3) manually enter the slope and intercept for a known calibration. For specific help in performing a new calibration, refer to the information sheet that came with each sensor. PZCALS.85p - This file contains the intercept and slope values for each Vernier analog probe. You can edit this file with the calibrations of your set of probes. PHZGRAPH.85p - This program performs various graphing functions. PHZMICRO.85p - This program is called when you select the Microphone from the list of probes. PHZMONIT.85p - This program is called when you want to monitor the readings from one or more channels. PHZOPTIO.85p - This program is used to select regions of data, determine integrals, and set experiment triggering. PHZTIMEG.85p - This program produces graphs of active channels as a function of time. If only one probe is active, a real time graph can be displayed on the calculator as the data is collected. If more than one channel is active, a real time graph will not be available. You will have to wait until the data collection is done in order to see the graphs. PHZTRIGG.85p - This program supports the trigger/prompt and trigger data collection modes. Each time you press the [TRIGGER] button data is stored in the CBL. In the trigger/prompt mode you will be prompted for an independent variable. In the trigger mode, you will not be prompted for a variable. XI. POSSIBLE ACTIVITIES Here is a list of possible experiments to perform with this program and the appropriate sensor or sensors. 1) Suspend a mass from a spring above a Motion Detector. (To protect the Motion Detector, place an upside-down wire "in-basket" over the Motion Detector. The wire basket will not interfere with the operation of the Motion Detector but it will stop freely falling masses.) Use a small sample time such as 0.04 s to collect data as the mass undergoes simple harmonic motion. If you choose to collect data without a live display, you will have access to distance vs. time, velocity vs. time and acceleration vs. time graphs. Study the phase relationships between distance, velocity and acceleration. Model the distance vs. time data with a sine function. Change the spring or mass to determine the effect of these variables on the period. 2) Perform the above experiment but suspend the spring and mass from a Student Force Sensor. Force data will be collected along with distance, velocity and acceleration. Compare the acceleration to the applied force. 3) A Motion Detector and Student Force Sensor can be used to investigate impulse and change in momentum as a dynamics cart bounces off the Force Sensor. Position the Motion Detector so it can measure the cart’s velocity as it moves toward and away from the Force Sensor. The Motion Detector will allow you to determine the change in velocity while the Force Sensor will allow you to graph the change in force during collision. 4) Use the Motion Detector to study the motion of a volleyball as it is tossed straight in the air. Position the Motion Detector on the floor and again protect it with a wire in-basket. Use a 0.04 s sample time with 50 data points to perform a 2.0 s experiment. Stand to the side of the Motion Detector with the ball at arms length above the Motion Detector. When data collection begins, toss the ball straight upward. Use the select region option to view the parabolic curve. Model the distance vs. time graph with a quadratic function. Determine the coefficient of the x squared term. Model the velocity vs. time graph with a linear function. Determine the slope of the line. Compare this slope to the coefficient of the x squared term in the first model. How do these values compare to the acceleration due to gravity? 5) Use one or more Accelerometers to measure the linear acceleration while in a car, elevator or amusement ride. 6) Attach a CBL and Accelerometer to a remote control car to measure centripetal acceleration. Relate the centripetal acceleration to the car’s linear speed. 7) Use a tuning fork or tuning forks to collect waveforms. Use the Trace option to estimate the period of the signal and calculate the frequency. Use the frequency option in the program to compare the two methods of determining frequency. 8) An excellent activity involves applying a trigonometric model to sound data collected from tuning forks. To do this, collect a set of data using the waveform option in the MAIN MENU. Quit the program and press the [Y=] key. Notice that Y1 has been defined with the following equation: Y1=A*sin (2*pi*F*X +D). The variables, A, F, and D can be modified in attempting to match Y1 to the data. Estimates of A and F can be obtained by pressing the [GRAPH] button and redisplaying the last graph. Press the [TRACE] button and use the arrow keys to read off x and y values to estimate the amplitude, A, and to record the time between consecutive portions of the graph. The reciprocal of the period of the wave will approximate the frequency, F. Store those values in the A and F variables and again press the [GRAPH] button. Both the data and the modeling function will be graphed on the same axes. A, D and F can be fine tuned to improve the fit. More complex waveforms can be modeled, such as the superposition of two sine waves. 9) Tune a home-made musical instrument using either the waveform or frequency option in the program. For example, blow across the top of a soft drink bottle and adjust the water level in it to tune it to a tuning fork. Try to tune two bottles such that they are an octave apart. 10) Use the waveform option to compare the patterns produced by different musical instruments. 11) Use the waveform option to collect a waveform when two sound sources are played simultaneously. If they are slightly out of tune, the beat frequency can be determined from the graph. 12) Measure the speed of sound by capturing the waveform of a sound and its echo. Set up a 1 to 2 meter hollow tube like PVC pipe or a carpet role with a microphone placed at one of the openings. Block the other end or leave it open. Use the trigger/waveform option of this program so that it is ready to trigger on a sound. When you snap your fingers next to the microphone, the microphone will record a waveform showing the initial sound and the echo reflected from the other end. If the other end is unblocked, the echo will have the same shape as the initial sound; otherwise the echo will be inverted. While viewing the graph and noting the shapes of the sound and its echo, use the arrow keys to determine the time between the initial sound and the reflection. Use this time and the length of the tube to calculate the speed of sound. If the tube is longer than 2 m, you may need to increase the time between samples in order to see the echo. See the section on editing the sample time. 13) Use the frequency mode to investigate the musical scales. Determine the frequency of the notes do, re, mi, fa, so, la, ti and do. For example, you might use an electronic keyboard and measure the frequencies of middle C and the next seven white keys up the scale. Determine the ratio of the note’s frequency to the starting note. The theoretical ratios are 1/1, 9/8, 5/4, 4/3, 3/2, 5/3, 15/8, and 2/1. Compare the ratios of consecutive notes to theoretical values of 9/8, 10/9, 16/15, 9/8, 10/9, 9/8, 16/15. XII. PROGRAM DESIGN NOTES These programs have been written to support Texas Instruments and Vernier probes with the CBL. We hope they help you perform a variety of experiments with this exciting technology. Please feel free to share these program with other teachers and students. Hopefully they have been written in such a way that you can modify them for your particular application. The programs were designed and written by Rick Sorensen and Matthew Denton. Please contact us if you have any questions concerning these programs or the use of our probes with the programs. October 23, 1996 Rick Sorensen Matthew Denton Vernier Software 8565 S.W. Beaverton-Hillsdale Hwy. Portland, OR 97225-2429 (503) 297-5317 email: rsorensen@vernier.com