Lab 1

Laboratory exercises are not just about getting the right result, but about recognizing that fundamental physics principles shape our everyday experiences and underlie many of the devices that we use in our personal and professional lives.  Please do not treat the laboratories as cookbook exercises.  Permit yourself to think!   Thoughtful answers to the questions in blue will give you most of the laboratory credit.

You can discuss the lab with your fellow students and the lab instructors in the Canvas discussion forum.

Open a Microsoft Word document to keep a log of your experimental procedures and your results.  This log will form the basis of your lab report.  Address the points highlighted in blue.

Grading scheme for all labs:


Install the app PhyPhox on your smartphone (iPhone or Andoid).  It gives you access to most of the sensors in your phone and has setups for many experiments.  Explore some of the measurement that you can make with this app.  It will be helpful in some of the later labs.

Introduction to the tools

Exercise 1

Your main tool for analyzing data will be the Microsoft Excel spreadsheet program.  Let us go ahead and start using it.

Assume you have performed an experiment, measuring the position of an object moving along a straight-line path as a function of time.  Your data are shown in the table below.  You suspect that the object moved with constant speed, covering equal distance in equal time intervals.  You want to verify this by producing a plot of position versus time and confirming that it is well-fitted by a straight line.  If yes, then the slope of the straight line is equal the speed of the object in units of m/s.

Time (s)  Position (m) 
0 0.00
1.5 2.64
3 5.22
4.5 7.61
6 10.22
7.5 12.84
9 15.43
10.5 17.98
12 20.52
13.5 23.03
15 25.37

Basic instructions for producing the plot are given below.  Experiment with the various options Excel presents to you.

(a)  Open Excel and enter your data.

(b)  Produce a graph of position versus time.

(c)  Study your graph.  The plot of position versus time should resemble a straight line.  The slope of the best fitting straight line should yield the average speed of the object.  You can find this slope by adding a trendline to your graph. 

(d)  The fit is not perfect.  The data you have collected contain experimental uncertainties.  To find the resulting uncertainty in the slope you must use the regression function.

Note:  The trendline is the best fitting straight line to the data.  It is the same line you get from the regression function line fit plot.  The slope of this trendline is your best estimate of the average speed.
The statistical uncertainty in the average speed is the standard error in the slope you get from the regression function.  This uncertainty only includes the error due to the scatter in the data points, not any systematic error, such as a calibration error.

Paste your labeled plot of position versus time (including the trendline) into your Word document and answer the questions below.

To practice entering and copying formulas, let us calculate the speed of the object for each small time interval from the raw data.

We want cell C2 to hold the speed of the object between t = 0 and t = 1 s.  Speed is distance covered divided by the time interval.  The distance covered is the difference between the entries in cells B3 and B2 and the time interval is the difference between the entries in cells A3 and A2.

Construct a plot of speed versus time.  Let us use the a method that does not depend on the data occupying adjacent columns.

Paste your labeled plot of speed versus time into your Word document.

There is a huge scatter in the values, because of experimental uncertainties in the measurements of small distances and time intervals.  But if we make many measurements we expect the average of these uncertainties to decrease with the number of measurements.  (The fitting routine producing the trendline averages over all data points and therefore produces a speed value with a much smaller uncertainty.)

Let us find the average value of all entries in column C.

What is the value of the average speed?  How does it compare to the slope of the straight-line fit?

Understanding Motion - Distance and Time

Exercise 2

Sometimes the best way to measure the position of a moving object as a function of time is to make a video recording and then analyze the video clip.  In this exercise you will analyze a clip showing a cart moving on an air track.  You will determine the position of the cart as a function of time by stepping through the video clip frame-by-frame and by reading the time and the position coordinates of the cart off each frame.  You will construct a spreadsheet with columns for time and position, and a plot of position of the cart versus time.

To play the video clip or to step through it frame-by-frame click the "Begin" button.  The "Video Analysis" web page will open.  You can toggle between the current page and the "Video Analysis" page.

Paste your labeled plot of x(m) versus time (s) (including the trendline) into your Word document and answer the questions below.


Exercise 3

Use an on-line simulation from the University of Colorado PhET group to explore vector addition.
Click HERE to open the simulation.

Click the "Lab" image.  Explore the interface

Use the simulation to solve the following problems:

(a)  You walk 15.5 m in a direction 14.9o North of East.
Use the simulation to represent your displacement vector.

(b) To get to a restaurant, you leave home and drive 9 miles South and then 17 miles West.
Use the simulation to represent your displacement vector.

(c) Suppose you and a friend are test-driving a new car.  You drive out of the car dealership and go 12 miles East, and then 5 miles South.  Then, your friend drives 15 miles West, and 10 miles North.

(d)  An airplane is flying North with a velocity of 200 m/s with respect to the air.  A strong wind is blowing East at 30 m/s with respect to the ground.

Convert your log into a lab report.  See the grading scheme for all lab reports.

E-mail address:

Laboratory 1 Report

Save your Word document (your name_lab1.docx), go to Canvas, Assignments, Lab 1, and submit your document.