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Main » Kinematics & Dynamics » Understanding Motion » Offline Activities » Lab I.1.3

### Motion Lab I.1.3

Purpose:

To determine the type of motion of a disc on an air hockey table by analyzing the speed of the disc.

Materials:
 » Air Hockey Table » Stroboscopic lamp » Straw » Meter stick » Polaroid camera » Tripod » Graph Paper

Background Info:

To find the average speed at the beginning and the end of the disc's path we need to measure both distance traveled and the change in time. An air hockey table is useful since very little friction is present and the motion is in a straight line. A hand held stroboscope would allow the students to view the motion; however you would not be able to analyze a photograph with this method.
If the required equipment is not available, students may use the photograph included to conduct the analysis.

Procedure:

1. Attach the straw to the disc and set up the meter stick on the table so that it can measure the distance traveled by the disc when it rebounds.
2. Mount the camera on the tripod. The shutter speed needs to be set on time exposure.
3. Turn on the stroboscopic lamp and set it to flash 10 times per second.
4. Shoot the disc. When it rebounds from one end, press the shutter release on the camera and hold it down until the disc passes by the ruler. After the picture has been developed you will notice that the time interval between images is equal to the time interval between stroboscopic flashes (0.10s).

Data & Analysis:

1. Determine the average speed of the disc at the beginning of the experiment. To do this divide the distance traveled between flash 1 and 2 by the time elapsed (0.01s). Don't forget your units.
2. Determine the average speed of the disc at the end of the experiment. To do this measure the distance between the last two flashes and divide this by the time elapsed (0.01s). Don't forget your units.
3. Compare your results. What properties are necessary for an object to have uniform motion? Is the motion of the disc uniform? Explain.

Conclusion: Remember your conclusion must respond to the purpose.

Extension: This extension will help to develop organization skills and will introduce the importance of graphing.

1. Construct a table with the following headings:
 Number of the Flash Time (s) Distance (cm) 0 0 0 1 0.1 . 2 0.2 . . . . . . .

2. Construct a distance-time graph. Plot time in seconds on the horizontal axis and position in centimeters on the vertical axis. [ General Graphing ]
1. What is the shape of the resulting graph?
2. The slope of a straight line distance-time graph is equal to the average speed of the object. Determine the average speed of the disc. Compare this answer to your previously calculated average speeds.