Physics 1 Lab #2: Position - Time Graphing Download a pdf of this lab here. Physics 1 Position - Time Graphing Introduction: Graphing is one of the most common and useful ways to display data. Graphing produces a picture of a process. It shows you what is happening. Looking at numbers can't give you the same information that a graph can. Graphing Position vs. Time: Position is a measurement showing where an object is located compared to another object or point. You can measure how far away an object is from a given point, along a straight line. This is called one-dimensional displacement. We will be working with one-dimensional displacement in this activity. Purpose of Activity: To investigate the rate of change of position of an object moving with uniform motion, and to investigate the graph of such motion. Reference: Before doing this activity, you should have Read chapter 2, sections 2.1 and 2.2 in College Physics, Wilson & Buffa, 6th Ed. Done the Chapter Outline for Sections 2.1 and 2.2, including objectives, vocabulary and Questions 1 â 5. Equipment: Air track, glider, small masses, electronic photogates Procedure: The air track is a triangular tube, angled on the top, with small holes drilled down the sides. It is marked off in centimeters, and a red metal glider fits the angled top. Air blows through the small holes drilled in the air track. The glider rides on a cushion of air. This reduces the friction between the glider and the track to almost zero. We will attach a small mass to the glider and allow the mass to pull the glider for a very short time. When the mass stops pulling, the glider will continue to move. We will measure this motion with photogates. The picture on the right is a photogate. A red line shows where a small light beam shines. Breaking this light beam starts or stops a timer. We can use the photogates to precisely measure the time it takes for a glider to travel a distance. 1 of 6 3/10/08 9:00 PM

Data: Trial 1 1. A small mass will provide the force to start the glider moving. Choose a mass, and stay with it. Do not change masses in the middle of the experiment. 2. We will set the first photogate at 30 cm on the air track. We will leave it there for this entire experiment. When the glider passes the first photogate, the timer will start. 3. We will set the second photogate at different distances. When the glider passes the second photogate, the timer will stop. 4. We will do six trials. The second photogate will be moved farther away from the first one in each successive trial. For each trial, you will do three time measurements and average them. 5. Use Microsoft Excel to create your data tables. (Excel is on all of the computers in the NLC, and in the physics lab. Excel is found on both Macintosh computers and PCs.) Save these tables; you will include them in your lab report. 6. When you have all of your distances and times, you will make a graph. You will put position on the y-axis and time on the x-axis. Use Microsoft Excel to make your graph. 7. Calculate the slope of the line on your graph. Trial 2 2 of 6 3/10/08 9:00 PM

Trial 3 Trial 4 Trial 5 3 of 6 3/10/08 9:00 PM

Trial 6 Summarize the data from the tables above. Trial Position 1 Position 2 Δx (cm) Time (s) Avg. Time (s) 1 4 of 6 3/10/08 9:00 PM

2 3 4 5 6 1. Calculate the speed of the glider for each trial. Speed is defined as the distance that the glider travels each second. So: 2. Enter the speeds in this table: Trial Δx (cm) Avg. Time (s) Speed (m/s) 1 2 3 4 5 6 5 of 6 3/10/08 9:00 PM

3. Graph this information. Put Δx on the y-axis and time on the x-axis. In your results section, describe the shape of the line you get. 4. Calculate the slope of this line. 5. Compare the slope of the line with the speeds that you calculated above. Conclusions: Re-read the purpose of this experiment. What did you learn from this experiment that answers the question in the purpose? 6 of 6 3/10/08 9:00 PM