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18
G
ETTING
S
TARTED WITH THE
CBR 2™
S
ONIC
M
OTION
D
ETECTOR
©
2000
V
ERNIER
S
OFTWARE
&
T
ECHNOLOGY
Activity 3—A Speedy Slide
Notes for Teachers
Concepts
Function explored: parabolic
The motion of sliding down a playground slide is used
to illustrate the real-world concept of changing
velocity due to friction.
Materials
Ÿ
calculator (see page 2 for available models)
Ÿ
CBR 2™ motion detector
Ÿ
unit-to-CBR 2™ or I/O unit-to-unit cable
Ÿ
EasyData application or RANGER program
Ÿ
Playground slide
Hints
The use of a playground area with several slides is
preferable for this experiment. The slides should be
straight. Slides with other shapes could be used in an
extension. For safety reasons, remind your students
not to attempt to pass each other while on the slide
steps.
You may wish to carry the interfaces, calculators, and
motion detectors to the playground area in a box or
boxes, and distribute the equipment to your students
there. Remind your students that the Motion Detector
does not properly detect objects closer than 15cm.
Depending on the type of slides that are available, you
may wish to change the way your students position
themselves for data collection. Some slides have large
platforms where the student with the Motion
Detector and the student with the calculator and
interface can be located.
Students can use wax paper, slippery cloth, sand, and
other materials to increase their speed. To enable your
students to be prepared, be sure to alert them to Part
II in advance.
Typical plots
A Speedy Slide
Typical answers
1. See the Sample Results.
2. In the Sample Results, the Part 2 speed was 0.90
m/sec greater than the Part 1 speed. Wax paper
was used to decrease friction and increase speed.
3. Answers will vary. Speeds will differ because of
differences such as contact area, weight,
streamlining, and the use of low-friction materials.
4. Answers will vary.
5. Increasing the height of the slide should increase
speed.
6. The stone dropped from the top of the slide
should hit the ground first because friction and the
incline of the slide slow the rolling stone more.
7. The level part at the bottom of a slide slows sliders
and prevents injuries.
Extensions
Design and carry out a plan to measure speed or
velocity on a different piece of playground equipment.
Have a contest to see who in the class or group can
obtain the greatest speed going down a slide.
Sample results
Speed (m/sec)
Trial 1
Trial 2
Trial 3
Average
Part 1
1.97 2.02 2.00 2.00
Part 2
2.80 3.07 2.82 2.90