In this exercise you will analyze two video clip. One clip shows a person riding a bicycle and the other shows a person riding a motorcycle. You will determine the position of the bicycle or the motorcycle as a function of time by stepping through the video clip frame-by-frame and by reading the time and the position coordinates of the bicycle off each frame. You will construct a spreadsheet with columns for time and position and use this spreadsheet to calculate the average speed of the bicycle over given time intervals.
To play the first video clip or to step through it frame-by-frame click the "Begin" button. The "Video Analysis" web page will open. You can toggle between the current page and the "Video Analysis" page by pressing Alt-Tab.
 | Play the video clip. When finished, the video clip will rewind automatically and stop at frame 0. |
| In the setup window choose to track the x-coordinate of one object. |
| Go to the "Take Data" window. Click "Start taking data". A spreadsheet will open up. |
Pick the point on the bicycle whose position you will track and position the cursor over that point. When you click the left mouse button, the time and the x-coordinate of your chosen point will be entered into the spreadsheet. (The x- and y-coordinates of the cursor (in units of pixels) are measured with respect to the lower-left corner of the frame.) You will automatically step to the next frame of the video clip.
| Position the cursor over the point you are tracking and click the left mouse button to enter the time and the x-coordinate of that point into the spreadsheet. |
| Repeat for each frame in the video clip. Then click "Stop Taking Data". |
| Go to frame 0 to see the calibration marker. It is a black line whose length is 1.72 m. |
| Go to the "Calibration" window and click "Calibrate x". |
| Position the cursor over the left end of the marker and click the left mouse button, then position it over the right end of the marker and click the left mouse button again. This will enter the x-coordinates of the ends of the marker into the boxes labeled "x1" and "x2". Enter the length of the marker (in m) into the box marked Dx, i.e. type 1.72 into the box marked Dx. Click "Done". |
| Click "Choose Origin". Choose a point to be the origin of your coordinate system, position the cursor over that point and click the left mouse button. This will enter the x-coordinate of this point into the box labeled "origin". Click "Done". |
| Click "Click to add calibrated columns". A new column will appear in your spreadsheet, giving the x-coordinates of your chosen points in units of meter with respect to your chosen origin. |
| Find the change in the position Dx = x2 - x1 of the bicycle over some time interval Dt = t2 - t1 by reading x1 at t1 and x2 at t2 off the spreadsheet |
| What is the average speed (in m/s) of the bicycle between 0s and 0.4s? |
| What is the average velocity (in m/s) of the bicycle between 0s and 0.4s? |
| What is the average speed (in m/s) of the bicycle between 0.4s and 0.8s? |
| What is the average velocity (in m/s) of the bicycle between 0.4s and 0.8s? |
| What is the approximate instantaneous velocity (in m/s) of the bicycle at 0.4s? |
| What is the average acceleration (in m/s2) of the bicycle between 0.4s and 0.8s? |
To earn extra credit analyze the second video clip. Click the "Begin" button below.
Open Microsoft Word and prepare a report using the template shown below.
Answer the following questions in complete sentences.
| What is the average speed (in m/s) of the motorcycle between 0s and 0.4s? |
| What is the average velocity (in m/s) of the motorcycle between 0s and 0.4s? |
| What is the average speed (in m/s) of the motorcycle between 0.4s and 0.8s? |
| What is the average velocity (in m/s) of the motorcycle between 0.4s and 0.8s? |
| What is the approximate instantaneous velocity (in m/s) of the motorcycle at 0.4s? |
| What is the average acceleration (in m/s) of the motorcycle between 0.4s and 0.8s? |
Save your Word document (your name_exm1.doc) and attach it to an e-mail message to your instructor.