Physics Laboratory
Horace Mann School
Lab 1:
Graphing Motion
Background :
We begin or journey in physics by studying the laws of motion. However, before we can do that, we need to develop a
clear way to describe the motion of objects. We call this subject kinematics. Furthermore, physics is a science based
on observation, so you are going to make some observations. In this lab you will observe the positions as a function of
time of several people walking or running at a constant velocity. For each person, you will make a plot of his or her
position as a function of time, and from that plot, you will determine each person’s velocity.
Experimental Procedure
Choose four “runners” whose motion will be the subject of your observations
Designate a “starter” and “recorder” for each group.
Everyone else will be a “timekeeper.”
Each timekeeper needs a stopwatch.
You will work in groups of at least seven people. All the timekeepers spread out along a straight line on a sidewalk or
in a hallway. Assign the timekeeper at one end of the line to position zero (the origin). Then, determine the positions
of all the other timekeepers (i.e., the distance from position zero). You may use whatever unit of distance you wish for
the timekeepers’ positions (e.g., feet, meters, blocks, light-years); however, you may want to use something
convenient!
The first three runners will start at the “beginning” (near position zero) of the line, walking or running at different,
constant speeds, and the fourth runner will start at the other end of the line and walk or run in the opposite direction at
a constant speed. Each timekeeper will note the time at which each runner passes by, and the recorders will record all
the data in a table. Note that before each runner starts, the timekeepers will need to synchronize their stopwatches.
Prior to taking data, each member of each group needs to prepare a data table. (Prepare this data table by hand.) A
good data table will include the following:
• A brief (one-sentence) description of what data is being presented in the table
• Column and/or row headings that make it clear what data is presented in each column or row
• Units for all data (the units can be included in the column or row heading)
• The names of everyone in the lab group
Analysis
Note: Each person is responsible for completing his or her own analysis.
1. Use the data to make a graph of the position of each runner as a function of time. Put all of the data on one graph.
Hint: what quantity should go on the horizontal axis? For the data for each runner, draw a best-fit line (using a ruler).
A good graph will include the following:
• A brief description what is being presented in the graph
• Labels for the axes, including units. Axes drawn with a ruler or other straight edge.
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A consistent scale that begins at zero and makes good use of the space available
Clearly labeled data points (you may use a legend for this) if you have multiple sets of data on one graph.
Don’t: Use breaks on the axes
Don’t: Connect the data points (this would imply you have measurements between the data points)
2. Using your graph, answer the following questions:
a) Is the relationship between position and time approximately linear, or would your data be better represented by
some other smooth curve (e.g. a parabola)?
b) Draw a best-fit line for each set of data and calculate the slope of those lines (do not use the data points, use
the actual lines).
c) What information does the slope of a position-vs-time graph provide?
d) What are the units of the slope?
e) What does it mean if the slope is negative?
f) What is the physical significance of the position-vs-time graph being a straight line?
3. Provide a table with the velocity of each runner, and include the appropriate number of significant figures.
Write Up
The following should be included in your write up:
• Your name, and the title of the lab.
• Your group’s data table. (Each person makes their own data table.)
• Your responses for the Analysis section. For questions that require written answers, your response must be in
complete sentences and stand on its own (i.e., the reader should not have to refer back to the question to make
sense of your answer). Do not write your answers on this sheet.