PHY 105 – Conceptual Physics

Kinesthetic Kinematics

Leader: _________________________ Recorder: ___________________________

Skeptic: ________________________ Motivator: __________________________

Materials

Laptop

LabPro

Motion Detector

Introduction

The purpose of this lab is to develop an understanding of the graphs of position vs. time and velocity vs. time and how they relate to different types of motion.

Background Information

Our procedure will be to record the position as a function of time using ourselves as the object of study. We will measure our position as a function of time using the LabPro interface and a sonic motion detector.

The sonic motion detector measures distances by making use of the fact that sound travels at a constant speed through the air. The sonic ranger measures position by emitting a brief pulse of ultrasound towards a target and then detecting the sound reflected from the target. The sonic ranger determines the time interval that passes between when the pulse of sound is emitted and the reflected sound returns. The distance is determined from d = v_st_r/2, where v_s is the speed of sound, and t_r is the time interval between when the sonic ranger emits a pulse of sound and when it detects the reflected sound. The result is divided by 2 because the time interval represents a round trip for the sound, and is thus double the distance to the target. The speed of sound depends on the temperature, but at room temperature, the speed is approximately 343 m/s.

Procedure

1. Set-up

The experimental set up is shown in figure 1. To set up the apparatus, plug the cable from the motion detector into the socket labeled DIG/SONIC 1 on the LabPro. Verify that the LabPro is plugged into the USB port of the computer and that it has power. Clamp the motion detector to a chair in a position such that the motion detector has an unobstructed view of you walking towards and away from the detector over a distance of several meters. The motion detector attaches to the clamp via a bushing on the back. Note that the motion detector will not allow you to measure distances of less than .5 m or greater than about 5 m.

2. Start the Software

In this class we will frequently use a program called LoggerPro. To launch LoggerPro, double click on the LoggerPro 3.1 icon (looks like the Jaws of a caliper) on the desktop. Once LoggerPro starts up, close the Tip of the Day box. LogerPro might then display a box labeled Connect to LabPro. If it does, click on the radio button labeled Connect onm Port: and choose LabPro – USB from the drop down box. Click OK to accept. If you have any difficulties notify your instructor.

To operate the motion detector, click on the Open folder . (Alternatively, you can choose the FILE menu, and then choose OPEN…) Find and open by double clicking the folder titled "_Physics with Computers". Double click on the File labeled "01a Graph Matching".

3. Test the Set-up

To verify that the apparatus is running correctly, we will make a quick graph of position versus time. The monitor should display a blank graph of Distance versus Time. On the right and above the graph is a small button labeled COLLECT . If you do not have a COLLECT button, or if the collect button is grayed out notify your instructor. Click on the COLLECT button. The motion detector should click twice, and then make a continuous clicking sound for ten seconds during which it is collecting data. Move back and forth in front of the ULI motion detector and verify that it is operating correctly. If not contact your instructor.

Figure 1

Apparatus for this experiment

4. Printing

One last thing we need to do is print our graphs. Click on the Printer Button on the tool bar. A window will appear labeled Printing Options. Click on the check box next to Footer and enter information to identify your graph as other groups will be printing very similar appearing graphs. Click OK when you're ready to print.

Report Format

Turn in one report worksheet with attached graphs for each group. Make sure that the name of each person in the group is put on the worksheet.

Report Worksheet

Leader: _________________________ Recorder: ___________________________

Skeptic: ________________________ Motivator: __________________________

Now that we have got our apparatus working, we will acquire the following pictures.

i) Construct a graph so that the position increases with a constant slope. a) Explain how you moved in order to achieve this result?

b) Discuss among your group and then sketch in the space below what you think a graph of the velocity vs. time should look like for this picture?

c) Once you started, did you accelerate during this motion? Explain.

Click on the Open icon. You will find that you are still in the "_Physics with Computers" folder. Double click on the file called "06 Ball Toss". When asked if you wish to save 01a Graph Matching, click on NO. In general, when LoggerPro asks you if you want to save a file, say NO. Move in the same way that you did to produce the first graph and observe the velocity and acceleration graphs.

d) Comment on how well your prediction in questions b) and c) compared to what you observed.

Attach one copy of the graph from EXP06.

ii) Open 01a Graph Matching again.

a) Discuss among your group how you will have to move so that the graph increases with a constant slope that is larger than in your first trial.

b) Carry out the motion and discuss if your group was correct.

iii) Construct a graph so that the position decreases with a constant slope. a) Explain how you moved in order to achieve this result?

b) Discuss among your group and then sketch in the space below what you think a graph of the velocity vs. time should look like for this picture?

c) Once you started, did you accelerate during this motion? Explain.

Open the experiment file titled "06 Ball Toss". Move in the same way that you did the produce the graph you just made and observe the velocity and acceleration graphs.

d) Comment on how well your prediction in questions b) and c) compared to what you observed.

Attach one copy of the graph of position vs. time and one copy of the graph from EXP06.

iv) Open 01a Graph Matching again.

a) Discuss among your group how you will have to move so that the graph decreases with a constant slope that is larger in magnitude than in your previous trial.

b) Carry out the motion and discuss if your group was correct.

v) Open the experiment file called "01b Graph matching". The idea is to try and move so that you match the graph. Have each member of your group try and match the graph. Print one copy and label on the graph the places where the velocity was positive, negative and zero.

Attach the labeled graph.

vi) Open the experiment file called "01d Graph Matching". The idea is to try and move so that you match the graph. Have each member of your group try and match the graph. Print one copy and label on the graph the places where the velocity was positive, negative and zero. Also label on the graph where acceleration occurred.