Lesson 1: Introduction to Motion

Goals

• Highlight value of diversity in the discipline of physics

• Introduce the idea of scientific models

• Explore constant speed and it various representations (graphical, table of values, motion diagram, words)

• Check out Penny Oleksiak's gold medal-winning swimming race!

This lesson takes three classes!

The Gender Imbalance in Physics

We start of the motion lesson with a discussion of an important problem. Across Ontario, 40% of grade 11 physics students and 34% of grade 12 physics students are female. This is a problem that should be fixed! I address this early in our course with a short presentation on the value of diversity in scientific fields. I challenge all teachers to solve this problem in your own schools - it can be done! Read my article to find out how we did it.

Article: We Can Fix the Gender Imbalance in Physics

Penny's Gold Medal Swim Race

We start our motion unit with a real situation: Penny's Rio Olympics gold-medal race. It is no coincidence that we are focusing on the accomplishments of a female athlete. The study of motion should be both interesting and useful, so we begin with the context of sports scientists analyzing Penny's performance. 

One of our sports science goals is to determine how steady Penny's swimming is: her coach is very interested in this! This leads to a discussion of how to track her speed using distance and time measurements and how to make a decision: is she swimming with a constant speed? Notice how these familiar physics topics arise naturally from the scenario. Learning is much more interesting and successful when there is a genuine need for it! We are not just presenting a comprehensive summary of the physics knowledge students should acquire. We are helping them discover and assemble this knowledge in a context-rich situation where the new ideas have purpose and meaning.

Scientific Models

In this context we introduce the idea of scientific models: simplified pictures based on assumptions that we create in order to study the complex world around us. This is one of the most helpful ideas I have added to our physics program. The idea of models frames our thinking about problems in a scientific way and prevents us from thinking of it as a math problem with a bit of a story to it. I strongly encourage you to learn more about this from the article below!

Article: A New Approach to Teaching Motion: Modeling, Metacognition, and Mathematical Sense-Making

Testing a Claim

Scientific knowledge is useful; if it wasn't, we wouldn't be learning it! Students should experience this from the start of their physics course. Again, we provide a reason for the next bit of learning: to test an advertising claim that you can see in the slide to the right. Should we believe what we see on the internet? This motivates our introduction of position graphs, slope, and velocity. Using these tools and evidence the students collect, they can make a decision about these cars.

Testing a Model

Our speed measurement of the car and our ideas about how it moves constitute a scientific model. Models are useful if they help us understand and explain things or predict things. It is only by testing models that we refine and develop scientific knowledge. 

We give our students a "simple" task. Make measurements to find the speed of the constant speed car, and then use that speed to predict how much time it will take to travel between two marked positions along the track I have set up at the front of the room.  Easy, right? Not once you involve the real world!  Why is it challenging? These are the reasons:

• they have to decide how to find the speed

• they use too small a measurement interval so their uncertainties are large compared to the measured quantities

• they accidentally switch to a different car part way through!

• they are not told the distance long the track and have to find it

• the measuring tape attached to our table under the track does not start at zero!

• the data from the computer gives the start and end times, not the time interval

• the measured time interval never matches their prediction exactly, they have to decide if it's close enough (within +/- 0.5 s)

• every group's prediction (and car) is different

• there is no right answer to look up in a book

All of this is a lot like doing real science - because they are! They are starting to practice the thinking processes that scientists and engineers use. This is a much richer experience than a typical constant velocity physics lesson! Compare this with a task like: "The car travels a 75-m distance between two traffic lights with a speed of 20 m/s. How much time does this take?"