Physics Laboratory 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.


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.  Answer all questions.

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
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?


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 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.


Vectors

Exercise 3

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

Explore the interface

Use the simulation to solve the following problems:

(a)  You walk 30 m in a direction 30o North of East.

(b) To get to a restaurant, you leave home and drive 6 miles South and then 10 miles West.

(c) Suppose you and a friend are test driving a new car.  You drive out of the car dealership and go 10 miles East, and then 8 miles South.  Then, your friend drives 8 miles West, and 6 miles North.

(d)  An airplane is flying North with a velocity of 200 m/s. A strong wind is blowing East at 50 m/s.


Convert your log into a lab report.

Name:
E-mail address:

Laboratory 1 Report

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