Science Buddies: "Ask an Expert"

So I`m doing the project of Using the Solar & Heliospheric Observatory Satellite (SOHO) to measure the Motion of a Coronal Mass Ejection. Ok this is a lot I don`t understand most of it. IDon`t understand how to get the average velocity ( a= v2-v1/t2-t1) I don`t know what to put and how to find the what measurements etc in the formula also I don`t understand how to find the acceleration etc I am really confused on what numbers measurements to put in the formulas and what to measure. Also the Time interval and screen position, actual position in the chart what????? will I understand what to put there once I figure out the rest
please help!!!!!!!!!

Avenged_101,

Welcome to the forum and thanks for your question. Once you have a series of SOHO images (the project suggests 5) you need to determine an easily identified structure of the CME that you can see in all images. You will then relate the motion of that structure from one image to the next. So for any 2 images you will need to do the following and record it on the table in the project.

1) you need to find the diameter of the sun in the pictures. You can do this by printing the pictures out and using a ruler. You divide this number by the actual size of the sun which is 1.4 million km.
2) you measure the distance from the edge of the sun in image to the structure you selected earlier using your ruler. You find the actual distance of the structure from the sun by dividing your ruler measurements by the number you got from step 1 above. Do this for each image.
3) select 2 images in the sequence. To find the average velocity you take the actual position in image 2 and subtract the actual position in image 2: (s2 - s1). Then you find the amount of time that has passed between these two pictures by subtracting the time in image 1 from the time in image 2: (t2 - t1). Take the position difference you found and divide it by the time difference: v = (s2 - s1)/(t2 - t1). Do this to find the average velocity between all your images (between 1 and 2, between 2 and 3, 3 and 4, and 4 and 5).
4) find the average acceleration by taking the average velocity between images 1 and 2 and between 2 and 3 to be your velocity 1 and 2. Your time 1 can be the time of image 2 and time 2 can be the time of image 4. Subtract velocity found between image 2 and 3 from velocity between image 1 and 2: (v2 - v1). Subtract time of image 2 from image 4: (t4 - t2). Then divide time from velocity: a = (v2 - v1)/(t4 - t2). Do this so you have numbers representing the velocities and acceleration between each of your 5 images. You can average these together to get a final average of each parameter.

Remember to keep unit agreement. Distances should be in km and time should be in seconds.