# Stopping Distance Lab by HC120730114744

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```									                              Stopping Distance Lab

Objectives
- convert between different units for quantities
- Identify values of quantities and results of calculations to the appropriate
number of significant figures
- Distinguish between random uncertainties and systematic errors.
- State random uncertainty as an uncertainty range
- Draw and analyze qualitative graphs
- Transform equations into generic straight line form

Prediction
Do you think that there is a relationship between the stopping distance of a car
and its speed just before the brakes were applied? If yes, what do you think that
relationship might be? (It is Ok to use your drivers education manual if you wish)

Equipment
Track with Scale, Ruler, Vernier Lab-Pro, Photogate, Cylindrical Mass

Directions
1. Plug Photogate into dig/sonic 1. Set up photogate horizontally so that the
body of the cylinder slides between ends.
2. Open - Applications – Logger Pro 3 – File Open – Experiments – Probes and
Sensors – Photogates – One Gate Timer
3. Select - Experiment (top menu bar) – Set up sensors – Lab Pro 1 - click the
photogate icon in DIG/SONIC 1. – select Gate Timing - Choose Set
Distance or Length – for length of object enter width of your sliding mass in
m – ok – close
4. Press collect and push the mass in a straight line along the track and let go
before it moves through the photogate.
5. Record the velocity (from logger pro data table) and measure the distance
from the photogate to the point where the mass stopped sliding.
6. Repeat pushing the mass through the photogate (you don’t have to press
collect again) until you have a range of measurements (at least 7)

Graph Plotting
1. Unplug the Lab Pro USB cable from the computer
2. Open up Logger Pro 3 again
3. Type your velocity and sliding distance data into the data table
4. Put title, axes labels and units on your graph. Enter your group members
names as a footnote
5. Go to options – graph options – deselect connect points
6. Go to analyze – curve fit – select a function – try fit. Press ok when good fit.
7. Print out graph and data table on one sheet in landscape orientation
Analysis Questions
1. What is the mathematical relationship between stopping distance and initial
2. If you were traveling twice as fast in your car how much further would it take
you to stop? Explain!
3. Discuss possible sources of systematic and random error in this
experiment.
4. If you plotted stopping distance on the y-axis what would you plot on the x-
axis to produce a straight line graph?
5. What do you think braking distance depends on other than initial speed?
Think about what we tried to hold constant in this experiment (at least two).

Scoring Summary
1. Student has made a prediction and explained their answer                    _________ (2)
2. Student has a data table and graph on one sheet fully labeled
Graph includes at least 7 data points and an appropriate best-fit
curve with equation box                                                     _________ (10)
3. Student has described the mathematical relationship (linear, inverse..)
and compared with their prediction                                          _________ (2)
4. Student has used their relationship to explain what effect doubling
speed would have on stopping distance                                       _________ (2)
5. Student has discussed sources of systematic and random error                _________ (2)
6. Student has stated what needs to be on the x-axis to produce a
straight line graph                                                         _________ (2)
7. Student has stated at least two things that stopping distance depends
on other than initial speed                                                 _________ (2)

total _______ (22)

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