Lab report template
A science lab report with purpose, hypothesis, materials, procedure, data table, results, analysis and conclusion, numbered the way teachers grade it.
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Follow your teacher's rubric
Section names and order vary by teacher: some want Introduction instead of Purpose, some want Discussion as well as Analysis, and college courses often ask for an abstract. The nine sections here are the common high school order. Download the DOCX and rename a heading when your rubric says so.
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Lab Report
How the length of a pendulum affects its period
| Title | How the length of a pendulum affects its period | ||
|---|---|---|---|
| Course and teacher | Physics 1, Period 3, Mr. Park | ||
| Date | October 15, 2026 | Student | Jordan Lee |
| Lab partners | Taylor Kim, Casey Nguyen | ||
1. Purpose
To find out how the length of a simple pendulum changes the time it takes to complete one full swing (its period), and to compare the measured periods with the values predicted by T = 2 pi sqrt(L / g).
2. Hypothesis
If the length of the pendulum is increased, then the period will increase, because a longer pendulum has farther to travel on each swing and the restoring force per unit of displacement is smaller.
3. Materials
- String, 1.5 m
- 50 g hooked mass
- Ring stand with clamp
- Meter stick
- Stopwatch (0.01 s)
- Protractor
4. Procedure
- 1. Tie the mass to the string and clamp the string to the ring stand so the pendulum hangs freely.
- 2. Measure the length from the pivot to the center of the mass and set it to 0.25 m.
- 3. Pull the mass to one side to 10 degrees, measured with the protractor, and release without pushing.
- 4. Start the stopwatch as the mass passes the lowest point and time 10 full swings. Divide by 10 for the period.
- 5. Repeat the timing twice more at the same length.
- 6. Change the length to 0.50 m, 0.75 m and 1.00 m and repeat steps 3 to 5.
5. Data
| Length (m) | Trial 1, 10 swings (s) | Trial 2 (s) | Trial 3 (s) | Average period (s) |
|---|---|---|---|---|
| 25 | 10.1 | 10.0 | 10.2 | 1.01 |
| 50 | 14.2 | 14.1 | 14.3 | 1.42 |
| 75 | 17.3 | 17.5 | 17.4 | 1.74 |
| 00 | 20.1 | 19.9 | 20.0 | 2.00 |
6. Results and calculations
Average period = (trial 1 + trial 2 + trial 3) / 3 / 10.
Predicted period T = 2 pi sqrt(L / 9.81): 0.25 m gives 1.00 s, 0.50 m gives 1.42 s, 0.75 m gives 1.74 s, 1.00 m gives 2.01 s.
Percent error at 1.00 m = |2.00 - 2.01| / 2.01 x 100 = 0.5 percent. The largest error was 1 percent at 0.25 m.
7. Analysis
The period grew as the length grew, but not in proportion: doubling the length from 0.50 m to 1.00 m made the period about 1.4 times longer, not twice as long. That matches the square root in the formula. A graph of period squared against length is a straight line through the origin, which is what the formula predicts.
The biggest source of error was starting and stopping the stopwatch by hand, about 0.2 s per run, which is why we timed 10 swings instead of one. We also could not keep the release angle at exactly 10 degrees every time.
8. Conclusion
The hypothesis was supported: a longer pendulum has a longer period, and the measured periods were within 1 percent of the values predicted by T = 2 pi sqrt(L / g). The period depends on the square root of the length, so doubling the length increases the period by a factor of about 1.41. Mass and small release angles did not affect the result in this range. A next step would be to test whether the period changes at larger angles, where the formula is known to break down.
9. Sources
- Class textbook, chapter 11, Simple harmonic motion.
- Lab handout: Pendulum period, Physics 1, Fall 2026.
How to use it
Fill in the title, course, date and names, then write each section in its box. Materials and sources are one item per line; procedure is one step per line and the steps are numbered for you. The data table is typed as text: the first line names the columns, every later line is one row, with cells separated by a vertical bar. Results, analysis and conclusion are plain paragraphs.
Write the purpose and hypothesis before the lab, the materials and procedure during it, and the rest after. The report prints with numbered headings in the order most teachers grade: purpose, hypothesis, materials, procedure, data, results, analysis, conclusion, sources.
Things to watch
Keep results and analysis apart: results say what the numbers were, analysis says what they mean and where the error came from. A conclusion that says "the experiment was a success" earns little; one that says whether the hypothesis was supported, by how much, and what to test next earns the points. When a graph is required, make it in a spreadsheet and attach it; the data table here holds the numbers behind it.
Calculators that go with this
Frequently asked questions
What is the difference between results and analysis?
Results report: the averages, the calculations, the percent error, with one worked example of each formula. Analysis interprets: the pattern in the data, whether it matches the theory, and the sources of error ranked by how much they mattered.
How do I write the hypothesis?
If (what you change), then (what you expect to happen), because (the reason you expect it). A hypothesis can be wrong; a report whose data refute the hypothesis is still a complete report if the conclusion says so.
Can I add a graph?
Not inside the page builder. Make the graph in Excel or Google Sheets, export it as an image and paste it into the DOCX under the Data heading, or attach it as a separate page.
Is what I type saved anywhere?
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