# How to Write a Lab Report

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• Published : March 24, 2013

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How to write a lab report

Let’s take as an example a free-fall experiment. You drop a small steel ball from various heights and use an electronic timer to measure how long it takes the ball to hit the ground. From this you calculate the final speed of the ball using v = 2x/t.

You believe that the ball will have a constant acceleration of “g,” 9.8 m/s2. This will be seen if you graph velocity vs. time and get a straight line with a slope of 9.8. You end up with a table of data giving distances and fall times and a graph of v(t).

Audience

Before you start writing, you have to know what audience you’re writing for. You are writing for a fellow student who has not done this lab. You will assume he has about the same knowledge of physics as you do. You need to give him enough information to do the following:

Understand what you are trying to accomplish and how.
Evaluate how accurate and reliable your measurements are. •Evaluate the results of the experiment.
Reproduce the experiment himself.

Format

Now you have to write the report. The report will always have the same format with four sections (for physics 111 and physics 120/125) or five sections (for physics 185/280/285). Each section should be labeled exactly as shown below. A lab report should be as brief as possible without leaving out anything important. Use complete sentences and the best spelling and grammar you can.

Section 1: Theory

Describe the purpose of the lab. This may be one or more of three things:

You are trying to prove a theory. In our case we’re trying to show that the acceleration of a body in free-fall is constant. •You are examining a relationship. This is what you do if you don’t have a theory. For example if you measure the time it takes a pendulum to make one swing as you vary the size of the swing, but without having a theory or formula that allows you to make a prediction in advance. •You are measuring a...