“(...) the way in which science subjects are taught has a great influence on students' attitudes towards science and on their motivation to study and, consequently, their achievement.”

Encouraging STEM studies for the Labour Market (European Parliament)

When students solve a "traditional" physics problem, they are usually given a clearly defined situation with all the information they need. Consequently most of the time the way of solving these problems is very mechanical: they just have to look for a mathematical expression that matches the description of the problem, then they substitute the given data, and finally they solve the equation to obtain the numerical solution.

In this Instructable we are going to present an alternative way of posing a problem. Instead of giving a verbal, well-defined description of the problem, the students watch a video from which they must extract information to obtain the answer. The problems thus posed are usually poorly defined, such as those presented in real life. Besides, the video can provide more data than necessary, and other data may be missing. Therefore with this approach the students must have a more critical and active attitude. They analyze the problem from different angles to find possible ways to solve it, they decide which of these methods is the most suitable to obtain the solution, they look for the missing information, and finally, they solve it and evaluate the results.

In this activity we will show an example of the use of video to solve a specific problem about dynamics, but you can adapt it to a wide variety of other mechanics topics: kinematics in one and two dimensions, circular motion, rotational dynamics, Newton’s laws, conservation of mechanical energy, simple harmonic motion…

### Grades

Secondary education (15-18 years)

### Physics concepts

- Resultant force
- Newton’s second law
- Uniformly accelerated rectilinear motion
- Distance-time and speed-time graphs

### Material

Computer with a video analysis tool. The following options are free to download and use:

- Tracker Video Analysis and Modeling Tool (Windows, Mac OSX and Linux): https://physlets.org/tracker/
- Kinovea (Windows): https://www.kinovea.org/

## Step 1: Motivation

This text and video can serve as a motivating introduction for the students:

*The European satellite Gaia is entrusted with an unprecedented mission: to analyze a billion stars in the Milky Way to build the most comprehensive and precise three-dimensional map of our galaxy. With its two powerful telescopes, Gaia will not only monitor the motion, luminosity, temperature and composition of its target stars with an accuracy never before reached—it is capable of measuring the diameter of a human hair from a distance of 1,000 kilometers—but is as well expected to discover hundreds of thousands of new celestial objects. All the data collected by Gaia will help us understand the origin, structure, and evolution of the Milky Way.*

*Gaia has been launched on a Soyuz-STB/Fregat-MT rocket from the European Spaceport in Kourou, French Guiana, on December 19, 2013.*

Video: "Gaia: launch to orbit" https://www.youtube.com/watch?v=9XcJ1wFRCk8

After they have read the text and watched the video, the teacher asks the students how much they know about telescopes, rockets or space research, and starts a group discussion about these topics.

More information about Gaia:

- Inside Gaia’s billion-pixel camera (video with Spanish and English subtitles): https://www.youtube.com/watch?v=2r4owXLoXc0
- Gaia overview: http://www.esa.int/Our_Activities/Space_Science/Gaia/Gaia_overview

More information about launch vehicles: