Physics Lab Report Format and Example

Writing a physics lab report is an essential skill for students and researchers, as it demonstrates not only the results of an experiment but also the reasoning and process behind it. A well-structured report communicates the purpose of the study, the methods used, the data collected, and the conclusions drawn. It serves as both a record of work completed and a tool for others to understand and replicate the experiment. Many learners struggle with how to organize their findings in a clear and scientific format, which makes examples especially valuable. By reviewing a physics lab report example, students can see how to format sections such as the introduction, procedure, results, and discussion.

Structure of a Physics Lab Report

1. Title Page

This page makes your report easy to identify.

• Title of the Experiment: Be specific (e.g., “Determining the Acceleration due to Gravity using a Simple Pendulum” instead of “Pendulum Lab”).
• Your Name and the Names of Your Lab Partners.
• Course Name and Code (e.g., Physics 101).
• Instructor’s Name.
• Date the Experiment was Performed.
• Lab Section or TA’s Name (if applicable).

2. Abstract

A concise summary of the entire report (typically 100-200 words). It should be written last. A good abstract answers these questions:

• Objective: What was the main goal of the experiment?
• Method: Briefly, what did you do? (e.g., “We measured the period of oscillation of a pendulum for various lengths.”)
• Key Results: What was the most important numerical finding? (e.g., “The measured value for gravitational acceleration was g=9.82±0.15 m/s2g=9.82±0.15m/s2.”)
• Conclusion: What is the significance of your result? Did it agree with the expected/theoretical value?

3. Introduction / Objective

This section sets the stage.

• Background Theory: Briefly explain the physical principles and relevant equations behind the experiment. Define key terms.
• Objective / Hypothesis: State the specific purpose of the lab. What relationship are you investigating? If applicable, state your hypothesis—a testable prediction of what you expect to find.

4. Theory

This section provides the mathematical foundation for your experiment.

• Relevant Equations: List and clearly explain all key formulas you will be using. Define every variable.
• Derivations (if necessary): If you need to manipulate equations to get a form useful for analysis (e.g., deriving the slope of a line to represent a physical constant), show the steps here.

5. Experimental Procedure / Methods

Describe how you performed the experiment. The goal is to provide enough detail that someone else could replicate your work.

• Apparatus / Equipment: List all equipment used, including specific models and precision (e.g., “Vernier caliper with 0.05 mm precision,” “mass set,” “photogate timer”).
• Diagram: Include a neat, labeled diagram of the experimental setup.
• Steps in Your Own Words: Do not copy the lab manual verbatim. Write a concise, paragraph-form description of the steps you took. Mention how you controlled variables, what you measured, and how many trials you performed.

6. Data and Results

This section presents your raw and processed data objectively, without interpretation.

• Raw Data Tables: Present all your initial measurements in clear, well-labeled tables. Include units and measurement uncertainties for every data point.
• Sample Calculations: Show one complete, step-by-step example of each type of calculation you performed. This includes calculating averages, uncertainties, using formulas from the theory section, etc.
• Processed Data: If you have derived quantities (e.g., velocity from distance and time), present them in a separate table.
• Graphs (if applicable): This is often the most important part. Graphs should have a title, labeled axes with units, clearly marked data points, and a line or curve of best fit. Include the equation of the best-fit line and the R2R2 value.

7. Analysis and Discussion

This is the most important section, where you interpret your results and discuss their meaning.

• Interpret Results: Explain what your graphs and calculated values mean. What is the physical significance of the slope or intercept of your best-fit line?
• Error Analysis: This is crucial. Identify potential sources of error (both random and systematic). Do not just say “human error”; be specific (e.g., “air resistance affected the falling object,” “friction in the pulley was not accounted for”).
• Compare to Theory/Expected Value: Compare your final result (e.g., your calculated value of gg) to the accepted/theoretical value. Calculate the percent error or discrepancy.
• Uncertainty: Discuss whether your measured uncertainty (error bars) accounts for the difference between your result and the expected value. Was the difference significant?

8. Conclusion

Briefly summarize the experiment and its outcomes.

• Restate the Objective: Briefly remind the reader of the goal.
• Summarize Key Findings: State your final result clearly.
• State Whether the Objective Was Met: Did your results support the initial hypothesis?
• Suggest Improvements: Based on your error analysis, suggest specific ways the experiment could be improved in the future to reduce uncertainty or minimize systematic errors.

9. References

List any sources you consulted, such as your lab manual, textbook, or other scientific literature. Use a consistent citation style (e.g., APA, MLA).

10. Appendices (if necessary)

Include any material that is too lengthy or detailed for the main body of the report, such as:

• Extensive raw data sheets.
• Complex derivations.
• Code used for data analysis.

Example of a Physics Lab Report

Title: Determination of the Acceleration due to Gravity using a Simple Pendulum

Author: Taurus Nein
Lab Partners: Brandy Kurt, Emily Chen
Course: PHYS 101 – General Physics I
Instructor: Dr. A. Einstein
Date of Experiment: September 25, 2024
Lab Section: L02

Abstract

The objective of this experiment was to measure the acceleration due to gravity, gg, by investigating the relationship between the period and length of a simple pendulum. The period of oscillation was measured for five different pendulum lengths. A graph of the period squared (T2T2) versus the length (LL) was plotted and found to be linear, consistent with the theoretical model T2=(4π2/g)LT2=(4π2/g)L. The slope of the best-fit line through the data points was 4.02±0.03 s2/m4.02±0.03s2/m.

Using this slope, the value of gg was calculated to be 9.81±0.07 m/s29.81±0.07m/s2. This result is in excellent agreement with the accepted value of 9.80 m/s29.80m/s2, with a percent error of only 0.10%. The experiment successfully demonstrated the dependence of a pendulum’s period on its length and provided an accurate measurement of the gravitational acceleration.

1. Introduction / Objective

A simple pendulum consists of a small, dense mass (a “bob”) suspended from a light, inextensible string. When displaced from its equilibrium position and released, it undergoes simple harmonic motion for small angular displacements. The primary objective of this lab is to verify the theoretical relationship between the period of a simple pendulum and its length, and to use this relationship to determine the value of the acceleration due to gravity, gg, at our location.

Hypothesis: It is hypothesized that the square of the period (T2T2) will be directly proportional to the length of the pendulum (LL), and that the value of gg derived from this relationship will be consistent with the accepted value of approximately 9.8 m/s29.8m/s2.

2. Theory

The period TT of a simple pendulum—the time for one complete oscillation—is given by the formula:T=2πLgT=2πgL​​

where:

• TT is the period in seconds (s),
• LL is the length of the pendulum in meters (m),
• gg is the acceleration due to gravity in meters per second squared (m/s²).

This formula is derived for the ideal case of a point mass and a massless string, with “small” amplitude oscillations (typically less than 10 degrees).

To linearize the relationship for graphical analysis, we can square both sides of the equation:T2=(4π2g)LT2=(g4π2​)L

This equation has the form y=mx+by=mx+b, where:

• y=T2y=T2
• m=4π2gm=g4π2​ (the slope)
• x=Lx=L
• b=0b=0 (the y-intercept)

Therefore, a graph of T2T2 versus LL should yield a straight line through the origin. The acceleration due to gravity can be calculated from the slope mm of the best-fit line:g=4π2mg=m4π2​

3. Experimental Procedure / Methods

Apparatus:

• Pendulum clamp stand
• String (~1.5 m long)
• Metal bob (50 g mass)
• Meter stick (precision: ±0.1 cm)
• Digital stopwatch (precision: ±0.01 s)
• Protractor

Diagram:

(A simple sketch would be inserted here.)

text

      /|
     / |
    /  | L (length of string)
   /   |
  /    |
 /θ    |
/______|_________
       O  (bob)

Caption: Diagram of the simple pendulum setup. Length L is measured from the pivot point to the center of the bob.

Procedure:

1. The pendulum was set up by attaching one end of the string to the clamp and the other end to the metal bob.
2. The length LL of the pendulum was measured from the pivot point to the center of the bob using the meter stick. The uncertainty in length was estimated to be ±0.2 cm, due to the difficulty of aligning the meter stick with the pivot point.
3. For the first trial length (0.400 m), the bob was displaced to an angle of approximately 10° and released gently.
4. The time for 20 complete oscillations was measured using the stopwatch. This method of measuring multiple cycles reduces the error associated with human reaction time.
5. Step 4 was repeated two more times for the same length, and the average time for 20 oscillations was recorded.
6. The period TT was calculated by dividing the average time for 20 oscillations by 20.
7. Steps 2-6 were repeated for four additional pendulum lengths (0.600 m, 0.800 m, 1.000 m, and 1.200 m).

4. Data and Results

Table 1: Raw and Processed Data for Pendulum Oscillations
*Uncertainties: δL = ±0.0002 m, δT (from std. dev. of average) ~ ±0.004 s.*

Length, L (m)	Time for 20 Oscillations, t20t20​ (s)	Average t20t20​ (s)	Period, T (s)	Period Squared, T2T2 (s²)
0.4000	25.52, 25.48, 25.61	25.54	1.277	1.630
0.6000	31.18, 31.25, 31.09	31.17	1.559	2.430
0.8000	35.94, 36.01, 35.88	35.94	1.797	3.229
1.0000	40.20, 40.15, 40.32	40.22	2.011	4.044
1.2000	44.08, 44.20, 43.99	44.09	2.205	4.862

Sample Calculation:
For L = 0.4000 m:

• Average t20=(25.52+25.48+25.61)/3=25.54 st20​=(25.52+25.48+25.61)/3=25.54s
• Period, T=Average t2020=25.54 s20=1.277 sT=20Average t20​​=2025.54s​=1.277s
• Period Squared, T2=(1.277)2=1.630 s2T2=(1.277)2=1.630s2

Graph 1: Period Squared vs. Pendulum Length

(A graph would be inserted here with the following characteristics:)

• Title: Graph of T2T2 vs. LL for a Simple Pendulum
• X-axis: Length, L (m)
• Y-axis: Period Squared, T2T2 (s²)
• Data Points: Five points plotting (L, T²) from Table 1.
• Best-Fit Line: A straight line determined by linear regression.

The equation of the best-fit line obtained from linear regression is:T2=(4.02 s2/m)⋅L+0.007 s2T2=(4.02s2/m)⋅L+0.007s2

The slope of the line is m=4.02 s2/mm=4.02s2/m. The correlation coefficient is R2=0.9998R2=0.9998, indicating a very strong linear relationship.

Calculation of g:
Using the slope m=4.02 s2/mm=4.02s2/m:g=4π2m=4(3.1416)24.02=39.484.02=9.81 m/s2g=m4π2​=4.024(3.1416)2​=4.0239.48​=9.81m/s2

5. Analysis and Discussion

The graph of T2T2 versus LL produced a straight line with a very high correlation coefficient (R2=0.9998R2=0.9998), strongly supporting the theoretical prediction that T2∝LT2∝L. The small, non-zero y-intercept (0.007 s²) is likely due to systematic error, such as the finite size of the bob or a small offset in the measurement of the string length.

The slope of the line was determined to be m=4.02 s2/mm=4.02s2/m. Using this value, the acceleration due to gravity was calculated to be g=9.81 m/s2g=9.81m/s2.

Error Analysis:
The uncertainty in the slope (δmδm) was determined from the linear regression analysis to be ±0.03 s²/m. The propagated uncertainty in gg is calculated as follows:δg=g⋅δmm=9.81⋅0.034.02=0.07 m/s2δg=g⋅mδm​=9.81⋅4.020.03​=0.07m/s2

Therefore, the final result is g=9.81±0.07 m/s2g=9.81±0.07m/s2.

The accepted value for gg is 9.80 m/s29.80m/s2. The discrepancy between our measured value and the accepted value is:Discrepancy=∣9.81−9.80∣=0.01 m/s2Discrepancy=∣9.81−9.80∣=0.01m/s2

This discrepancy is well within our stated uncertainty of ±0.07 m/s². The percent error is:%Error=∣9.81−9.80∣9.80×100%=0.10%%Error=9.80∣9.81−9.80∣​×100%=0.10%

This exceptionally low percent error indicates a very accurate experiment.

Potential sources of error include:

1. Systematic Errors: The length measurement may have been consistently slightly off if not measured from the true pivot point. The pendulum may not have been a perfect “simple” pendulum due to the string having mass and the bob having size.
2. Random Errors: The dominant random error was human reaction time in starting and stopping the stopwatch. This was mitigated by timing 20 oscillations. Air resistance may have played a very minor role.

6. Conclusion

The experiment successfully achieved its objective. The hypothesized linear relationship between T2T2 and LL was confirmed, and the value of the acceleration due to gravity was determined to be g=9.81±0.07 m/s2g=9.81±0.07m/s2. This result is in excellent agreement with the accepted value of 9.80 m/s29.80m/s2, validating the theoretical model for a simple pendulum.

To improve the experiment in the future, a photogate timer could be used to measure the period with greater precision and eliminate human reaction time error. Furthermore, more careful measurement of the effective pendulum length, accounting for the radius of the bob, could reduce systematic error.

References

1. Physics 101 Lab Manual, “Experiment 3: The Simple Pendulum,” University of Example, 2024.
2. Walker, J., Halliday, D., & Resnick, R. (2018). Fundamentals of Physics (11th ed.), Chapter 15. John Wiley & Sons.

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