Keep On Truckin. by Nathan Cotten. Physical Science, Science as Inquiry. Grade Level. Louisiana Curriculum Framework Content Strand:

Transcription

1 Keep On Truckin by Nathan Cotten Louisiana Curriculum Framework Content Strand: Physical Science, Science as Inquiry Grade Level 9 Objectives: The students will be able to: use a TI 83+ Graphing Calculator, CBL 2 interface, and a Motion Detector to measure velocity record data and graph results determine the relationship between velocity and release point Teacher Information Benchmarks SI-H-A1, A2, A3, A7, SI-H-B3, B4, PS-H-E2 Curriculum Integration Safety Scientific method Laboratory procedures Lab reports Cross Curriculum Integration Physics Math Driver s education Applications Students can apply this activity to: driving on different road surfaces friction between two surfaces velocity of moving objects Time Frame This activity with assessment takes 90 minutes. Materials CBL 2 interface TI 83+ graphing calculator DataMate program Vernier motion detector Ramp (at least 1 m) Car with card attached Meter stick Books to support ramp Masking tape Large book Materials for surfaces - Astroturf, carpet, sandpaper, cotton fabric, plain wood Student Groupings Students will be cooperatively grouped into 7 groups. Each group will have no more than 4 students each. Each student is assigned a role: Captain, Co-Captain, Materials Manager, and Recorder.

2 Possible Obstacles to Student Learning prior knowledge of velocity use of technology measurement skills graphing skills Opportunities for Assessment Individual laboratory reports Post laboratory questions Test questions: students are required to manipulate technology in a laboratory practicum. Mid-term and/or Final Exam

3 Lesson Procedure Keep on Truckin Velocity is a rate that tells how much distance is covered in a unit of time. It can be expressed by the formula v = d/t where v = velocity or speed (in m/s), d = distance traveled (in meters), and t = time (in sec). In this activity, you will study the velocity of a car traveling over various surfaces after it is released from a certain point on a ramp. A Motion Detector will be used to measure velocity. HYPOTHESIS Figure 1 1. Predict which surface will allow the car to travel the most efficient (fastest) down the ramp. Rank in order of fastest to slowest. Fastest Slowest PROCEDURE 1. Set up a ramp on books as shown in Figure 1. The high end of the ramp should be 10 cm from the floor. Place a large book on the floor 1 m from the bottom end of ramp. This book will stop your car after it comes from the ramp. 2. Attach the Motion Detector upright at the top and center of the ramp. 3. Tape a card to the back of a car. The card serves as an ultrasound reflector. 4. Connect the Vernier Motion Detector to the DIG/SONIC port of the CBL 2 interface. Use the link cable to connect the interface to the TI Graphing Calculator. Firmly press in the cable ends. 5. Turn on the calculator and start the DATAMATE program by pressing APPS. Select DATAMATE by pressing 4. Press CLEAR to reset the program. (DATAMATE automatically sets up the motion detector sensor). 6. Setup the graph type by pressing 1 from the menu. Press to arrow down to MODE and press ENTER. 7. Select TIME GRAPH by pressing 2. Select CHANGE TIME SETTINGS by pressing 2 again.

4 8. Enter 0.2 as the time between samples in seconds. Enter 15 as the number of samples. 9. Select OK by pressing 1. Select OK again by pressing Place your car on the ramp with its front at the 1 m line. Select START to begin collecting data by pressing 2. Release the cart after the CBL2 beeps. Note: The Motion Detector starts to click. Get your hand out of the Motion Detector s path quickly. Stay clear of the area in front of the Motion Detector while the green light is flashing. 11. Determine the car s velocity. a. To see your velocity graph, press to select DIG-VELOCITY and press ENTER. If the displayed graph is not smooth (only one crest), press ENTER and redo the trial. Select MAIN SCREEN by pressing 1 and return to step 10. b. Use to examine data points along the graph. As you move the cursor right and left, the time (X) and velocity (Y) values of each data point are displayed below the graph. The highest point on the graph corresponds to the maximum velocity of the car. Record this maximum velocity in your data table. Round to the nearest 0.01 m/s. (In the example to the right, the maximum velocity is 1.45 m/s.) 9. Do two more trials with the same surface. a. Press ENTER, then select MAIN SCREEN by pressing 1. b. Repeat Steps two more times for a total of three trials. 10. Repeat Steps 6-9 for each surface provided by your instructor. DATA Data Table 1: Velocity of an Object on Various Surfaces 1. Surface Trial 1 (m/s) Trial 2 (m/s) Trial 3 (m/s) Average (m/s)

5 Attachments Attachment 1. Lab Report Rubric Attachment 2. Teachers Notes Exploration and Extension PROCESSING THE DATA 1. Calculate the average velocity for each ramp surface. Show your work below. Enter values in Data Table 1: Velocity of an Object on Various Surfaces 1) m/s 2) m/s 3) m/s 4) m/s 5) m/s 6) m/s 7) m/s 2. Construct a bar graph of the results on the graph paper provided. Plot SURFACE TYPE on the horizontal axis and VELOCITY (in m/s) on the vertical axis. 3. Compare the velocity of the car traveling on different surfaces. Include the most and least efficient surfaces. Compare these results to your hypothesis. 4. Why do the different surfaces cause the car to travel at various speeds? 5. Describe two ways you could make the car go down the ramp faster without changing the surface of the ramp or the release position. 6. Give two reasons why road surfaces are not made of the most efficient material(s) used in this experiment.

6 EXTENSIONS 1. Convert the Question 1 velocities to km/h and mi/h. 2. Calculate the acceleration of the car on each surface 3. Test the velocity of the car at different release points on the ramp. 4. Design an investigation to test the effect of streamlining on the velocity of a car traveling down a ramp. 5. Test the effect of placing weights at different positions on the car. 6. Have students graph data using Graphical Analysis for Windows

7 Attachment 1. Lab Report Rubric

8 Attachment 2. Teacher's Notes Teacher s Notes Boxes can be substituted for the books. Make sure the Motion Detector is positioned at least 45 cm from the car. The area in front of the Motion Detector must be free of obstacles (and students). ISCS cars or other skate-wheel cars work well. Toy cars with free-rolling wheels also work well. If small toy cars are used, you may want to tape two meter stick to a ramp and run the cars between them. If you use longer cars (or shorter ramps), you may find it necessary to change the release positions. Standard 7.5 cm x 12.5 cm cards (3 x 5 ) can be attached to the cars. The graph can be done by hand or using Vernier Graphical Analysis as mentioned in the extension. Frictional effects in this experiment cause the data to differ from the theoretical V 2 d relationship for a frictionless version of the experiment. Safety should always be exercised in every experiment. Have students obtain and wear goggles. References Volz, Donald, Sapatka, Sandy. (1998) Physical Science with Calculators, Experiment 36, pages 36-1 through 36-2T.