Instructions for Plotting Projectile Trajectory

  1. Save your .mpg file to the Desktop. This is important because, for some reason, Media Player doesn’t recognize a file on the floppy disk.
  2. Open Media Player.
  3. Select Media Library.
  4. Select All Video.
  5. Select +Add at top of window, then Add File or Playlist.
  6. Browse to your .mpg file on the Desktop and add it to the Video Playlist.
  7. Select the file, then select Play button at bottom of window to watch the 5 second movie. Click on the icon to make the image fill the screen. If you watch carefully you should be able to see the projectile trajectory. Observe the moving button at the bottom of the window as the movie plays.
  8. Select Play, then Pause immediately, before catapult ejects the projectile.
  9. Select a reference starting point at the level of the surface of the table below where you believe the projectile to leave the catapult. Measure the y coordinate of that point relative to the surface of the table in the picture. Use x=0 for the x coordinate.
  10. Click on right end of the moving button enough times to advance the movie to the first image of the projectile in flight. Measure the coordinates of the projectile.
  11. Measure and record on a spreadsheet, in millimeters, the x and y coordinates relative to the reference point of the projectile at each position it appears. Convert these measurements to actual trajectory coordinates by using the fact that the width of one section of white board is 2.45 meters or the height is 1.22 meters.
  12. Remove the .mpg file from the Desktop.
  13. Each team member should have a copy of the data. As a team, create the plot, examine the plot, and do the calculations to answer the questions below.

Homework: See the web course page for complete instructions. Each team member should do an individual report and demonstrate an understanding of what was done and of the results.

Questions:

  1. Using Excel, plot the trajectory (y versus x) using the data points adjusted to actual dimensions. Find the second-order polynomial best fit line to the points.
  2. What was the maximum height of the projectile?
  3. What was its initial angle, calculated from the coefficient of the x term of the polynomial?
  4. What was its initial velocity, calculated from the coefficient of the x2 of the polynomial?
  5. What was the range of the projectile?
  6. Assume that the velocity in the horizontal direction is constant and equal to the horizontal component of the initial velocity, i.e. v0x = v0*cos0. How long did it take for the projectile to reach maximum height? How long did it take to reach the target? Use 0.13 seconds between projectile images.