The Great Bungee Jump
Measuring with Video
Extension 4: 2-D with Video
Will the jumper crash into the building before reaching ground? To answer
this, we need to look at the two-dimensional motion of the bungee jump.
Our experiment was one-dimensional, looking just at the up-and-down motion
of the jumper. What about the horizontal motion?
Analyzing both kinds of motion requires a new king of measurment. Our wires
were good for one-dimensional motion, but cannot measure two dimensions
at the same time. Analyzing a video record is the best way to do this.
The idea is to make a video recording of the bungee jump. Click
here to download a sample video students made.
This recording can be digitized and analyzed by a computer using special
Video frames are 1/30 of a second apart. Using the computer, you can look
at each frame and locate the jumper. With the right software, you can click
on the jumper in each frame and automatically generate a table of time
and height. This is just the table generated by doing a different drop
for each line. Click here
for a table made from the sample video.
This technique is challenging because it is difficult to digitize video.
But if you can solve this problem, you will find that this is a powerful
and exciting way to do experiments. There are many other fast-moving events
you can analyze the same way, such as a diver, Magic Johnson, collisions,
or a rocket launch.
To collect data from video, you need:
- A video camera. You can record the motion with almost any video
camera. A tripod is handy to keep the camera steady.
- A digital video editing system. This is a computer equipped
with a special board for capturing video and turning it into a digital
form that can be saved on disk.
- Digital analysis software. This is special software that allows
you to pick out where the jumper is in each frame and convert your mouse
click to coordinates. We recommend two different packages: VIEW,
a free package from TERC and VideoPoint from Pasco.
Decide on your experiment and what equipment you will need. Before you
begin experimenting, tell your instructor what you plan.
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