Analyzing the motion of objects in free fall with video

What does the motion of an object in free fall on Earth look like? This question was pondered by great minds
such as Aristotle and Galileo. In this lab, you analyze videos that record the motion of falling objects from a set
height (5.56 m). This enables us to make a more accurate analysis of accelerating objects in the Earth’s gravitational
field, with and without the effects of air drag.
1. Go to the video playlist in the lab page on Canvas to preview all of the video clips that we’ll be analyzing, as if they
were made by your lab partners.
2. We are going to analyze each clip to find the fall time, tf , for each object: a heavy ball, a set of keys (twice), and
then a crumpled piece of paper. To do this, we first need to learn how to “step” through each clip frame-by-frame, and
to establish how many frames per second the video is played at. Proceed as follows.
Establishing the video frame rate “FPS” for timing:
Watch the first clip (on Canvas) of the red ball being dropped.
a. Go to the settings (gear wheel icon) below the video and select the highest quality (720p60 if available).
b. Let the clip play, but Pause it between 1 and 2 seconds. You can also slow down the video speed in Settings to make
this easier.
c. Use the period “.” key repeatedly to advance frame by frame, until the “seconds” timer below the video on the left
changes from 0:01/0:03 to 0:02/0:03. You can also use the comma “,” key to step backwards, if needed.
d. Now start counting “.” key presses as you advance the video frame-by-frame until the counter changes by 1 second
to 0:03/0:03. This will tell you the “FPS”, the number of frames per second. Record the value above the data table on
the next page. (This number is usually 60, but is sometimes 30 if you have a slower internet connection.)



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