Physics 201

Video Analysis Project

Your Task: Make a short video of some kind of two-dimensional motion (e.g. throwing a ball, jumping), and use the tools we have developed in this unit to represent that motion in various ways.The goal is to end up with an empirical model to describe the motion, and to evaluate whether or not the kinematics equations for constant acceleration (our theoretical model) can be applied for this system.

Examples of motions you could study:

  • Hitting a whiffle ball
  • Air pucks
  • Projectile launchers
  • Carts on tracks
  • Dropping coffee filters
  • Remote controlled car or helicopter

Your final report will include each of the following representations of motion, and will be written using the guidelines for a formal laboratory report(see back for details).

Representations of Motion:

  1. Verbal description. In words, describe the motion. Be as specific as possible.
  2. Dot diagrams and vectors. Use the video to make a dot diagram showing how the position changes over time. Explain how you decided where to draw the dot; which part of the object was the most important to follow? Draw displacement, velocity, and acceleration vectors on the dot diagram for each time interval.
  3. Graphical representations. Use Capstone to create position and velocity graphs based on your video. You will have four graphs total; two for the horizontal motion and two for the vertical motion.
  4. Mathematical representations. What equations can you use to describe the motion of your object? Write the equations describing how position and velocity change with time in both the horizontal and vertical directions (i.e. x(t) = …. Andy(t)=…….). These will be derived from the data you collect from your video. You will have one equation for each of the four graphs.

Some things to keep in mind when you are shooting your video:

  • You will need to know the length of some object in the movie so that you can set the scale for your measurements. The easiest way to do this is to place a meterstick in the field of view.
  • Try to keep all motion in a plane parallel to the camera to avoid parallax effects.
  • Don’t zoom in on the motion; keep the camera the same distance from the object at all times. I have a tripod you can use if you like.

Watch this tutorial for help with video analysis:

How do I turn this into a lab report? How is this a scientific investigation?

There are two ways to build mathematical models in physics:

  • Theoretical models start with basic physics principles and make some assumptions about a system to derive an equation.
  • Empirical models start with data and use the data to find an equation that describes the system.

What you have just done is derived an empirical model for the motion of your object. That means it is based on experimental data, and not derived from fundamental physics principles. We want to compare this to the kinematics equations for constant acceleration that we derived in class. The argument you build in your lab report should center around whether or not the kinematics equations can be used for this particular motion. To do this you will need to compare the theoretical and empirical models, and examine the assumptions and limitations of each.

Details on how to write a formal lab report and some comments on how to build a mathematical model are posted on Blackboard. It would be a good idea to read through this before starting your paper. Here are some additional notes that are specific to this project.

  • Abstract
  • Even though this is the first thing on the paper, it should be written last.
  • Include the purpose of the study, a brief summary of methods and results, and the significance of the result.
  • Introduction & Model
  • Start by describing the physical system that you chose to model. This is the verbal description from the list above.
  • Include the theoretical model (the constant acceleration equations) that we have been using to solve problems in class. Number all equations in the text.
  • Explain the limitations to this model, and make a prediction about whether or not you think they will hold for this motion.
  • Methods
  • Explain in narrative form how you collected and analyzed the data. Do no present the data.
  • Results & Analysis
  • Your results section should include:
  • The dot diagram from Capstone. You can capture this information as a screenshot.
  • Draw the displacement, velocity, and acceleration vectors on or near the dot diagram.
  • Position and velocity graphs. Include the best-fit curves, which represent your equations of motion.
  • Discussion
  • Your conclusion is the equations of motion that you derived from your data. Explain what the equations physically represent. In particular, what do the constants represent?
  • Discuss whether or not these equations are consistent with the constant acceleration equations we derived in class.
  • Explain how the experiment could be improved. This can include data collection, analysis, and model building.
  • References
  • You don’t need to find any extra references for this paper. You may wish to cite your class notes or the textbook or any other references you use. Use APA style.