How to Write a Good Lab Report - Department of Physics and Astronomy

1/1/24, 2:48 PM How to Write a Good Lab Report - Department of Physics and Astronomy https://physics.unc.edu/undergraduate/courses-credits-placement/sample-report/ 1/6 HOW TO WRITE A GOOD LAB REPORT SAMPLE LAB INSTRUCTION EXPERIMENTAL INVESTIGATION OF C/D Introduction: How is the circumference of a circle related to its diameter? In this lab, you design an experiment to test a hypothesis about the geometry of circles. This activity is an introduction to physics laboratory investigations. It is designed to give practice taking measurements, analyzing data, and drawing inferences without requiring any special knowledge about physics. EQUIPMENT (PER GROUP): Metric ruler Vernier calipers At least 5 objects with diameters ~1 cm to ~10 cm: (penny, marble, “D” cell, PVC cylinders) PROCEDURE: Design an experimental procedure to test the following hypothesis: Hypothesis: The circumference (C) of a circle is directly proportional to its diameter (D). This website uses cookies and similar technologies to understand visitor experiences. By using this website, you consent to UNC-Chapel Hill's cookie usage in accordance with their Privacy Notice.

1/1/24, 2:48 PM How to Write a Good Lab Report - Department of Physics and Astronomy https://physics.unc.edu/undergraduate/courses-credits-placement/sample-report/ 2/6 Make sure you record what you do as you do it, so that the procedure section of your report accurately and completely reflects what you did. Some helpful hints for taking and recording data are in the lab tips and in the grading rubric. ANALYSIS: Note: As the semester progresses, you will be expected to take more and more responsibility for deciding how to analyze your data. Drawing valid inferences from data is a vital skill for engineers and scientists. The instructions for analyzing data for most labs will not be as detailed as the instructions below. Numerical Analysis: Calculate the ratio C/D for each object. Estimate the precision of each value of C/D. Graphical Analysis: Use Excel to construct a graph of C versus D. Use Excel to display the equation of the best fit line through your data. Use the LINEST function to estimate the uncertainty in the slope and intercept of the best fit line. Make sure you interpret the meaning of both the slope and intercept. A checklist for graphs is in the grading rubric. Questions to consider: How do your calculations and graph support or refute the hypothesis? Does your graphical analysis agree with your calculations? Do your results for the C/D ratio agree with accepted theory? REPORT: A sample lab report for this activity is provided as an example for you to follow when writing future lab reports. SAMPLE LAB REPORT: EXPERIMENTAL INVESTIGATION OF C/D ABSTRACT In this investigation, we examined the hypothesis that the circumference (C) and diameter (D) of a circle are directly proportional. We measured the circumference and diameter of five circular objects ranging from 2 cm to 7 cm in diameter. Vernier calipers were used to measure the diameter of each object, and a piece of paper was wrapped around each cylinder to deterimine its circumference. Numerical analysis of these circular objects yielded the unitless C/D ratio of 3.14 ± 0.03, which is essentially constant and equal to π. This website uses cookies and similar technologies to understand visitor experiences. By using this website, you consent to UNC-Chapel Hill's cookie usage in accordance with their Privacy Notice.

1/1/24, 2:48 PM How to Write a Good Lab Report - Department of Physics and Astronomy https://physics.unc.edu/undergraduate/courses-credits-placement/sample-report/ 4/6 ANALYSIS: The C/D value for the penny is (5.93 cm)/(1.90 cm) = 3.12 (no units). The precision of the ratio can be estimated using the error propogation formula: Results for all five objects are given in the table below. Object Description Diameter (cm) Circumfer. (cm) C/D calculated (no units) Penny 1.90 ± 0.01 5.93 ± 0.03 3.12 ± 0.02 “D” cell battery 3.30 ± 0.02 10.45 ± 0.05 3.17 ± 0.02 PVC cylinder A 4.23 ± 0.02 13.30 ± 0.03 3.14 ± 0.02 PVC cylinder B 6.04 ± 0.02 18.45 ± 0.05 3.06 ± 0.01 Tomato soup can 6.6 ± 0.1 21.2 ± 0.1 3.21 ± 0.05 Average C/D = 3.14 ± 0.03, where 0.03 is the standard error of the 5 values. From this empirical investigation, the average C/D ratio is 3.14 ± 0.03 (no units). This ratio agrees with the accepted value of π (3.1415926…). The uncertainty associated with the average C/D ratio is the standard error of the five C/D values, which is equal to the standard deviation (0.06) divided by the square root of N, which in this case is 5 since there were five measurements. While the five C/D values do not agree within their estimated uncertainties, the variation between these values is relatively small (only about 0.06/3.14 = 2%), which suggests that the C/D ratio is a constant value. The reason for the imperfect agreement may be that the individual uncertainties were underestimated or perhaps is a consequence of the “paper” method used for measuring the diameters of the object. The paper may have slipped while we made the mark, but this “slip effect” should only be a random error, which would This website uses cookies and similar technologies to understand visitor experiences. By using this website, you consent to UNC-Chapel Hill's cookie usage in accordance with their Privacy Notice.

1/1/24, 2:48 PM How to Write a Good Lab Report - Department of Physics and Astronomy https://physics.unc.edu/undergraduate/courses-credits-placement/sample-report/ 5/6 not affect the average value of our measurements for C, since there is no reason to believe that the paper would have consistently slipped in the same direction (either too high or too low) every time. Another way to visualize and calculate this constant circle ratio is by graphing the circumference versus diameter for each object. Graphs are especially useful for examining possible trends over the range of measurements. If C is proportional to D, we should get a straight line through the origin. From our numerical results, we would expect the slope of the C vs. D graph to be equal to π. The slope of the best fit line is (3.15 ± 0.11), which is equal to π within its uncertainty. The intercept is essentially zero: (-0.05 ± 0.5). The R squared statistic shows that the data all This website uses cookies and similar technologies to understand visitor experiences. By using this website, you consent to UNC-Chapel Hill's cookie usage in accordance with their Privacy Notice.