1. Comparing Forces © Copyright 2014 – all rights reserved www.cpalms.org

2. Comparing Forces In this experiment you will use two force sensors to compare the force that one object exerts on another. The force sensors are electronic spring scales that use the strength of a magnetic force to measure force. Because the sensors use magnetic force, errors occur when the metal sensor ends touch each other. You will use graphs to look at both the direction of a force indicated by the + or -, and the amount of force indicated by how far the graph line is from the horizontal graph axis (0 force). © Copyright 2014 – all rights reserved www.cpalms.org

3. Cautions Do not exert too much force on the sensors. Watch the graphs and meters. If the graph line goes off the screen, or if the meter reads above 40 Newtons, decrease your force. Because the sensors only measure force along a straight line through the sensor, to get accurate measurements, make sure that the sensors are kept in-line with each other as shown. © Copyright 2014 – all rights reserved www.cpalms.org

4. Complete the PreLab Questions on your worksheet. 1) The force sensors use _______________________________ to measure force. 2) Because the force sensors use magnets, the _______________________ should not come in contact with each other. 3) If the scale reading goes higher than _________ Newtons, you should decrease the amount of force. 4) To measure accurately, the sensors must be kept ________________ with each other. 5) How does the graph show the direction of a force? 6) How does the graph show the amount of a force? © Copyright 2014 – all rights reserved www.cpalms.org

5. Procedure Open Logger Pro 3.4.1 on the computer that has the force sensors attached. Open the file “comparing forces” With the force sensors laying flat on the desk, and not pulling or pushing on anything, click the Ø button which is near the top left. This will open a window in which you can zero the force sensors. This tells the sensors what no force feels like. After zeroing the sensors, both meters should show 0 N. They will probably vary a little bit. © Copyright 2014 – all rights reserved www.cpalms.org

6. Procedure, pg 2 Determine which sensor is 1 and which is 2 by pushing or pulling on the eyehook and watching the meter. Connect the force sensors to each other with a doubled rubber band. Make sure during all data collections that the sensors stay flat on the table, and that they stay in line with each other. © Copyright 2014 – all rights reserved www.cpalms.org

7. Experiment 1 Hold sensor 1 in place. Click the “Start” arrow in the upper right of the screen. Pull sensor 2 away from sensor one, varying the stretch in the rubber band. Data will be collected for 10 seconds. On your data sheet, sketch the shapes of the graphs and answer the questions. Hold in place Pull © Copyright 2014 – all rights reserved www.cpalms.org

8. Experiment 2 Hold sensor 2 in place. Click the “Start” arrow in the upper right of the screen. Pull sensor 1 away from sensor one, varying the stretch in the rubber band. Data will be collected for 10 seconds. On your data sheet, sketch the shapes of the graphs and answer the questions. Hold in place Pull © Copyright 2014 – all rights reserved www.cpalms.org

9. Experiment 3 Click the “Start” arrow in the upper right of the screen. Pull both sensor 1 and sensor 2 away from each other, varying the stretch in the rubber band. Data will be collected for 10 seconds. On your data sheet, sketch the shapes of the graphs and answer the questions. Pull © Copyright 2014 – all rights reserved www.cpalms.org

10. Experiment 4 Click the “Start” arrow in the upper right of the screen. Use sensor 1 to pull sensor 2 across the table. Sensor 2 should resist, but move with sensor 1. Vary the stretch in the rubber band as you move. Data will be collected for 10 seconds. On your data sheet, sketch the shapes of the graphs and answer the questions. Follow with resistance Pull © Copyright 2014 – all rights reserved www.cpalms.org

11. Experiment 5 Click the “Start” arrow in the upper right of the screen. Use sensor 2 to pull sensor 1 across the table. Sensor 1 should resist, but move with sensor 2. Vary the stretch in the rubber band as you move. Data will be collected for 10 seconds. On your data sheet, sketch the shapes of the graphs and answer the questions. Follow with resistance Pull © Copyright 2014 – all rights reserved www.cpalms.org