A) Setting up and shutting down

Setting up

1. Plug in the cable from the Motion Detector into Digital/Sonic Port 1 on the Lab Pro Interface Box.
2. Log on to your NCSSM account.
3. Once the Windows NT desktop has appeared, click on the Start button in the lower left corner; then mouse-over Programs, Vernier Software, Logger Pro 2.0

1. Remove the Motion Detector cable from the Lab Pro box, being careful to press on the plastic tab of the connector while pulling out the cable.
2. Log off of your NCSSM account.
3. Put away any carts or inclined planes that you brought out.

1. Under Setup, select Sensors. Check that the following settings are present: D/S1 should have the sonic symbol; Motion Detector should be the sensor; Motion should be the Calibration. If any of these settings are incorrect, call the instructor over, otherwise click OK.
2. Under Experiments, choose Sampling. Change the Experiment Length to 5 seconds and the Sampling Speed to 10 samples/second. Click OK.
3. Under Window, go to New Tall Window and select Meter.
4. On the Meter Options under Select Meters, uncheck every box except Distance. Click OK.
5. Click the button labeled Collect. The distance meter will show the distance from the ranger to the nearest solid object in meters.
6. Your job in this part is to experimentally determine the approximate minimum and maximum distances that the sonic ranger measures correctly (allow for a 1 or 2 cm uncertainty). You'll need a meter stick to know the "accurate" distances. Record the results for the workable range of your Motion Detector in your lab journal. Check with the instructor to see if your answers are reasonable.

1. Decide which graphs to display. In general, you should always display the Distance (which really should be called "Position") graph, and you may add the Velocity and Acceleration graphs ONLY IF you have predicted them first in your lab book.
2. To remove graphs (you will need to do this initially so that only Distance is displayed), click on the graph you want to keep, usually the Distance graph. Then go to View and choose Graph Layout. Choose one pane.
3. To add graphs, go to View and choose Graph Layout. Choose two (or three) panes.
4. Double-click on the y-axis of the new graphs and choose your dependent variable, velocity or acceleration. De-select the variables you do not want to display. Click OK.
5. Double-click on the title and change it to the appropriate title, Velocity (or Acceleration) vs. Time.
6. To clear a data screen, Under Data, select Delete Run (Latest).

C) Position, time, & velocity

1) Remove the Digital-Live meter and the velocity and acceleration graphs, so that only the distance graph appears.

2. While standing still, aim the sonic ranger at a wall. Before asking the software to produce a graph of the wall’s position vs. time, predict what you think that graph will look like (don't worry about putting numbers on your axes; you only need to predict the shape of the graph). Make a sketch of your predicted graph in your lab journal at the top of a new page; use the whole top half of the page for this prediction and reserve the bottom half for the velocity vs. time graph that will come later. Label your axes: position and time.
3. Once you've predicted the shape of the graph, aim the sonic ranger at the wall and click on the Collect button to get the software to plot the graph. Does your prediction agree with the plot? To set the proper scaling, click on the vertical axis, then select Manual Scaling (under Axis Options) and type in 0 for the Minimum and 3 meters for the maximum.
4. You probably have some familiarity with the term velocity. What is the velocity of the wall (with respect to the sonic ranger) for the situation described in #2 above? What would the velocity vs. time graph for the wall look like? Make a prediction and sketch it in your lab book right below the position vs. time graph. Remember to label your axes with words.
5. We hope that you answered zero (or some equivalent) to the previous question. Now go back to the computer and check your prediction. The instructions for adding a graph are on the 1st page.
6. Look back at the position vs. time graph for the wall that you predicted and the computer plotted. Is there anything zero about the position vs. time graph? Talk it over with your partner.
7. We trust that your answer to the previous question, without looking ahead, was something like "the slope of the line or graph is zero." Now, is it a coincidence that both the velocity and the slope of the line are zero? In your lab journal, write a general definition of the slope of a line. Do not use the symbols x and/or y in your answer, but you may use words like horizontal, vertical, rise, and run. This is the last we'll remind you to write only in your lab journal. In the future, we expect you to do this automatically.
8. If we now apply your definition of slope specifically to a position vs. time graph, we see that the slope of the graph is the change in position divided by the change in time. And this is exactly the definition of velocity.
9. Now let's try something that moves. One person will walk away from the sonic ranger at a fairly slow constant rate. But before you try this, sketch a prediction of the position vs. time graph for the slow-walking person. Again, label the axes (but do not worry about numbers other than the origin on your graph). Compare your prediction to your partner's.
10. Now collect data -- but remember to turn the velocity vs. time graph off first (you haven’t predicted it yet, right?) The person who walks should begin at a distance from the sonic ranger that is roughly equal to the minimum distance for which the ranger works; you might also want to set the maximum distance to 3 meters. Record the computer-generated graph. Double-clicking on a graph allows you to select various options for that graph. NOTE: If you occasionally get spikes (exceptionally high or low points) on the graph, this is due to the failure of the ranger to detect your reflected signal. It sometimes helps to hold a reflector in front of the ranger as you are walking. This could be a book or other hard, flat surface.
11. Did your prediction match reality? Check with the instructor if you're not sure. Estimate the slope of the position vs. time graph by reading two ordered pairs (time, position) of coordinates at the opposite ends of your line and calculating the slope. Avoid using points that seem to be noticeably off from the general trend. To obtain coordinates, under Analyze, select Examine; then drag the mouse around your graph. Show your work, and include units (m, s, m/s) whenever you write a position, time, or velocity number.
12. Once you have calculated the slope of your position-vs-time graph: under Analyze, select Tangent. Then drag the mouse along your position-vs-time line. How do the Tangent values compare to the slope you calculated ?
13. Now for a new prediction. What would the velocity vs. time graph look like for the walk done above? Sketch your prediction (again, don't worry about numbers on your graph). (Hint: Was the velocity of the walker constant? How could you tell from the position vs. time graph?)
14. After you have sketched your velocity vs. time graph prediction in your lab book, go back to the computer and add the velocity vs. time graph. Leave the position vs. time graph on. You might also set the minimum velocity equal to zero and the maximum velocity equal to 2 m/s. Was your velocity vs. time graph prediction correct?
15. The other partner will now try a faster walk away from the sonic ranger. Before this happens, however, make a prediction of the position vs. time graph on the same axes as your previous prediction for the slow walk. Label the first prediction slow and the second one fast. Also predict the velocity vs. time graph (don’t worry about numbers here) for the fast walk and record it on the same velocity graph for the slow walk. Label both lines.
16. After predicting both position vs. time and velocity vs. time graphs for the fast walk, collect data for that walk, remembering to start at about the minimum working distance of the sonic ranger. Did your predictions match expectations?
17. Summarize what you have learned so far about how velocity information shows up on an object's position vs. time graph.

1. Use a dynamics cart, loaded with weights, for these activities. Set the ranger on the floor, aimed at the cardboard reflector taped to the back of the cart. Change the software settings to give you only a position vs. time graph; set the maximum position to 3 meters.
2. In this part you will give the cart a push away from the ranger. Try it first without the sonic ranger recording data (just turn the ranger face down on the floor temporarily). Then predict & obtain the position vs. time graph. If the cart slows down as it moves, how is that seen on the graph? Did it slow down?
3. Based on your position vs. time graph, predict what the velocity vs. time graph of the same motion would look like. (Hint: As the slope of the position vs. time graph changes, how does the velocity vs. time graph change?)
4. Turn on the velocity vs. time graph and check your prediction in 3). Sketch the graph you obtain. Were you correct?
5. When you compare the actual velocity vs. time graph to your prediction, you may find that the former has more irregularities than you might expect. This is due to the fact that the velocities are not measured directly by the ranger but instead are calculated by dividing the differences in position between successive data points by the corresponding time differences. Since the differences are quite small, substantial error is introduced into the calculated result. These errors show up as bumps and valleys in the graph. You should be looking for overall trends in the graph.
6. Next you'll look at a collision. If you push the cart so that the plunger end strikes a wall, the cart will push back off and return. Set up the ranger facing the wall and about 2 meters away. Put the cart about a half-meter from the ranger, ready to be pushed toward the wall. But wait! That's right, make your predictions of the position vs. time and velocity. vs. time graphs. (If you don’t think you can do both together, do the position one first, verify, and then predict the second.) You can, however, try the experiment without having the sonic ranger recording, if that will help you visualize the position and velocity graphs. Once you've predicted, push the cart and record results.
7. When the cart turned around at the wall, how did the position vs. time graph change? Be sure to be specific in discussing the slope of the line.
8. How did the velocity vs. time graph change? Again, be specific.
9. Something to note at this point is that changes of velocity are caused by the application of forces. When the moving cart slows down, that is due to frictional forces. When the cart changes direction, that is due to the push of the wall on the cart. (It may seem strange to think of a solid, immovable wall as exerting a push. Later we'll see that walls, floors, and other "immovable" objects can exert such forces.)
10. Something else to note is that there are two ways that velocity can change. One way is when the object speeds up or slows down. The other is when the object changes direction. You probably noticed that the velocity of the cart changed faster when it bounced off the wall than when it was slowing due to friction. This rate of change of velocity, termed acceleration, is investigated in the next section.

1. In this part, you'll look more closely at acceleration. Use the same cart as before, but allow it to roll down an inclined ramp. You'll find a variety of boards in the lab to serve as ramps. Start with an incline angle of just a few degrees. Continue to make predictions before performing each of the experiments.
2. Here, you'll start the cart at the top of the ramp. Position the sonic ranger aimed down the ramp so that the cart will move away from the ranger while rolling down the ramp. Obtain position vs. time and velocity vs. time graphs and record them. You may need to change scales if the maximum values are too small/large.
3. Describe in words each of the graphs you just obtained. Use words like constant, increasing, decreasing, slope, positive, negative, zero.
4. How do you think you could determine the acceleration of the cart? (Hint: Think about how you found velocity from a position vs. time graph. How can you find acceleration from a velocity vs. time graph?)
5. We hope that you realized that the slope of the line on the velocity vs. time graph is the acceleration. You can calculate a value for it by reading two (time, velocity) coordinate pairs from the graph and using the slope formula. Do that now, and be sure to carry units throughout the calculation. Note that the units of acceleration are m/s per s or m/s² for short. Once again, avoid using points that seem to not follow the overall trend.
6. Add a graph of acceleration vs. time below the velocity vs. time graph. You may see a lot of bumps in this graph, because the process of calculating accelerations from the velocity-time data introduces error in addition to those introduced in calculating velocities from the position-time data. Do any time intervals on the graph have constant acceleration?