PHYSICS ADV with Mr Regester

PHYSICS ADV with Mr Regester

LAB: Tracker analysis of falling objects NAME:______

You need:

·  Tracker, the video analysis program. Hit the link on the Tools link on our Haiku page, or directly enter http://www.cabrillo.edu/~dbrown/tracker/

·  The video shot in class, of a ball being tossed straight up. Right-click on the link and save to a folder on your computer.

I’ll show you how to use Tracker in class, but here is a quick reminder breakdown of the steps you need to follow:

  Open the video.

  Play the video. Find the interesting section (starting and ending frame numbers) you will analyze.

  In the “clip settings”, enter the start and ending frame numbers, and frame rate (frames per second).

  Insert a “calibration stick”, using an object of known length in the frame to set the scale.

  Insert coordinate axes. The default orientation has x horizontal and y vertical. Keep it that way.

  Create a new “point mass” track.

  Shift-click on the moving object in each frame of the clip, marking its location. When you are done, each location of the ball will be marked. Hit the Set Trail Length and Hide Numbering buttons so all the points are marked without numbers. Sketch the video frame in the space provided on page 2.

  The graph of x(t) will appear to the right of the video, but we’re not interested in the horizontal motion of the ball. Click the x on the vertical axis and change it to y, the vertical position of the ball. Sketch the plot in the space provided in page 2.

  Click the y on the vertical axis and change it to vy, the velocity of the ball in the vertical direction. Sketch the plot in the space provided on page 2.

  Right-click on the velocity graph and select Analyze...

  Press the Analyze button above the new, larger version of the graph, and check the Curve Fits box. The program will put a linear “best-fit” line matching the velocity. Write the equation for the best-fit line here: ______

Questions

What was vo, the initial velocity of the ball when it was released?

How much time did it take to reach its apogee?

How high did the ball go?

At what time after launch did the ball return to its launch position?

What was the ball’s velocity when it returned to its launch position?

Sketch video frame with projectile locations marked. / Sketch y(t) graph here.
Sketch vy(t) graph here.