 Worksheet 4.5

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 1. Your teacher will hand out a sequence of nine images from the RHESSI spacecraft as well as some graph paper. Examine each image and determine the location of the brightest spot in the coronal X-ray source (a.k.a. “the blob”), which is above the coronal loop. 2. Using a ruler, draw one horizontal and one vertical line through that spot (cross hairs) reaching the axes so that you can read off the coordinates of the spot. Record the data in the table provided below. 3. Determine the height of the blob above the surface of the Sun (in arc seconds). This can be done a number of ways. Discuss which ways are possible with your Science Team (and possibly your teacher) and decide how you will make this measurement. Describe your method below and show all calculations. Record the data in the table. 4. Convert the height that you calculated above from units of arc-seconds to kilometers. In all the images, the scale is 725 km/arc-sec. Show your calculations below and record the data in the table. 5. Plot the data on a graph above the surface of the sun. The x-axis should be Time and the y-axis should be Height in kilometers. Be sure to label the axes and include units. Do not draw lines through the points in the graph, just plot the points. 6. Return to the data table and calculate the distance moved between each pair of consecutive points. Show all work and record the data in the Table. 7. Use the distance moved between each pair of points and divide it by the time interval between each image to calculate the average speed of the blob at each point. Show all work and record the data in the Table. 8. Finally, use a ruler to draw a line through the last 3 points in your graph. If you cannot get a straight line to go through all three points, draw the line such that it comes as close to all three points as possible. Now, measure the slope of the line, displacement in the y-direction divided by the displacement in the x-direction (“rise over run”). The slope of this line is the average speed of the blob as it was ejected from the Sun. Show all work and record your result below. 9. When did the blob experience the greatest acceleration (change in velocity with time)? Explain. 10. When did the blob experience the greatest acceleration (change in speed with time)? Explain. 11. When did the blob experience the greatest net force, and what was the source of the force? Explain.
 Time Time Interval (sec) X-Ray Source Position Height (arc sec) Height (km) Distance Moved (km) Speed (km/s) X Y

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