Studio Session 1

Introduction to the tools

During this semester, you will use the Pasco 850 Universal interface connected to a computer and several software packages to collect and analyze data and present your results.  Most of the time, when doing experiments, you will work in groups of three.  Each group will have one Pasco 850 interface and two laptop computers to work with.  Students in a group will rotate through the various tasks to make sure each student is familiar with all aspects of each experiment and activity.  All students are required to participate in all activities and stay until the session is dismissed.  The 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.

Today you will familiarize yourself with some of the software and hardware tools you will use in your studio sessions.

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

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
1 0.8
2 1.5
3 1.6
4 2.5
5 2.7
6 3.2
7 3.9
8 4.5
9 5
10 5.5

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.

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?

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 the 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

imageIn the studio sessions you will also collect data using Pasco 850 interface and the Capstone software.  The Pasco 850 interface is a data acquisition system connected to the computer.  It can collect information from various analog and digital sensors, and generate seven different output signals.  This exercise will familiarize you with this data acquisition system.

imageThe instrument you will use today is the motion sensor.  The motion sensor is a sonar ranging device.  It uses pulses of ultrasound that reflect from an object to determine the position of the object.  Our motion sensor cannot accurately measure distances smaller than approximately 20 cm.

You will use the motion sensor to measure the position of a mass oscillating on a spring as a function of time.

Highlight your final graph in Capstone, click Edit, Copy, and then paste it into your word document.
Do you think you are now familiar enough to acquire data with the motion sensor without needing additional instructions?  Please comment.

Convert your log into a session report, certify with you signature that you have actively participated, and hand it to your instructor.