Department of Physics, The Chinese University of Hong Kong
Copyright © 2003 Education and Manpower Bureau, HKSAR
Activity: Displacement-time graph of Abyss Turbo Drop
Key Learning Points:
1. Velocity
2. Uniformly accelerated motion
3. Motion graphs
Introduction
Students will analyze the motion of the Abyss Turbo Drop by using the Motion Video
Analysis Software. A displacement-time graph of the motion will be plotted. They will
discuss the motion of the ride, divide the motion into several periods, and find out the
velocity or acceleration of the ride in each of these periods.
Background knowledge
Basics

Motion graphs of uniform motion and
uniformly accelerated motion.
Advanced

Slope of s-t graph = velocity.

s-t graph of uniformly accelerated motion
with non-zero initial velocity.

Finding velocity and acceleration by curve
fitting using a spreadsheet
Procedure
How do you feel when taking the Abyss
Turbo Drop?
Basics

Take a look at the ride at a distance. Take a
video of motion.

Use the Motion Video Analysis Software to plot a s-t graph of the ride.

Identify the time intervals corresponding to the different stages of the ride's motion.
Discuss the motion at each stage.
Advanced

Export the data using the software. Sort out the part of the data which describes the
passenger platform when it is (1) travelling upwards initially, (2) thrust downwards
for the first time.

Plot the displacement-time graphs for these two time intervals. Use a spreadsheet
(e.g. MS Excel) to fit data set (1) with a straight line and data set (2) with a
quadratic curve.

Discuss the motion for each of these time intervals.

Find out the velocity and acceleration with the software for each case.
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Department of Physics, The Chinese University of Hong Kong
Copyright © 2003 Education and Manpower Bureau, HKSAR
Discussion
Basics

Identity the time intervals corresponding to the different stages of the motion.
Which time interval corresponds to (a) initial rise? (b) brief stop at the top? (c) first
downward thrust? (d) subsequent rises and falls?

In which time interval(s) is the ride (a) travelling at a constant velocity? (b) at rest?
(c) accelerating? (d) decelerating?
Advanced
Based on the s-t graphs of (1) the initial rise and (2) the first downward thrust, answer
the following questions.

Is the velocity constant during the initial rise? How do you know? How do you
find the velocity of the initial rise?

How do you find the average acceleration of the first downward thrust?

Is the acceleration constant when the ride is thrust downwards? How do you know?
Fit the data with a cubic curve and discuss the result.
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Department of Physics, The Chinese University of Hong Kong
Copyright © 2003 Education and Manpower Bureau, HKSAR
Teachers' Notes
Typical Results
Velocity of initial rise = 2.2 ms-1
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Department of Physics, The Chinese University of Hong Kong
Copyright © 2003 Education and Manpower Bureau, HKSAR
Average acceleration = 2  (-3.837) ms-2 = 7.7 ms-2 (downwards)
Remarks:
In fact, the acceleration of the ride keeps changing when it is thrust downwards. The
downward acceleration is controlled by the difference in the tension of the upper and
lower cables connecting the passenger platform and could be much greater than g. So
strictly speaking, the downward motion is not a free fall with a constant acceleration.
One can see the change in acceleration in details by taking more data and fitting the data
with a cubic curve as below:
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Department of Physics, The Chinese University of Hong Kong
Copyright © 2003 Education and Manpower Bureau, HKSAR
It reveals that the initial acceleration is greater than g. The initial acceleration is about
2   7.5 ms -2  15 ms -2 . It is this acceleration that gives you the "negative g"
feeling. In a second after takeoff, the acceleration decreases to a smaller value and the
players will have a weightless feeling.
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