PASCO SE-9076 Constant Velocity Tubes User Manual
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Constant Velocity Tubes
012–06697B
Experiment 1: Constant Velocity Motion and the Linear Graph
Purpose
The purpose of this experiment is to study a rising bubble and to develop a quantitative description
of its motion.
Theory
Under a given set of conditions, the motion of a rising bubble is highly repeatable. At the most
basic level, describing motion involves describing position as a function of time. In this
experiment, variables that might conceivably affect the bubble’s motion, such as tube angle
and temperature, are held constant. Position data are recorded for a variety of times.
Before position data can been meaningful, a reference frame must be defined. For convenience,
the initial position of a moving object is often chosen to be zero. Since the initial position of the
bubble is concealed in this experiment, it is not possible to determine the initial position.
Instead, the end of a tube is defined as position zero, simply because this is a convenient place
to measure from. Given that the bubble moves upward, it is most convenient to define positions
above the end of the tube to be positive.
When the position–time data points from one of the tubes are graphed, a clear pattern to the
data can be clearly seen. Plotting data from other tubes on the same graph produces similar
patterns, but with distinctive differences that may be related to the differences in the motion.
The patterns that emerge are of a type familiar to algebra students, and an equation for each can
readily be written.
Procedure
➤ Follow your lab’s safety procedures, including wear-
ing safety glasses.
1. Obtain a tube which has one end wrapped in paper. Do not remove
the paper. Record the color of the fluid in the tube.
_____________________
2. Work with a partner to practice timing the motion of the bubble as
follows:
a)
Hold the tubing nearly horizontal, but with the wrapped
end slightly higher. Allow time for the bubble to travel as
far as it can under the paper wrapping (Figure 1) .
b)
Your partner should be watching the clock (or operating
the stopwatch). Choose a time interval that is long
Figure 1
wrapped
end