A physics lesson in speed and velocity – Part 1

Let me walk you thru a session with my children on (un) teaching them basic concepts of speed and velocity… thru a series of posts.

At the end of the posts I will deconstruct the method behind this approach.

Scene 1: Luke Skywalker gets on his pod. He needs to get to the Sand Dunes on the planet of Tatooine. He travels north for 3 Kms. At the Dulcos pass he takes a left turn to go west. He then travels 5 Kms. At that point he suspects that the sand people may be stalking the area ahead. So he turns north again and travels for 7 Kms. He then reaches the Sand Dunes of Tatooine.

  1. Can you draw the journey? Make sure you draw the pod, sand people and the mountains. Any other aliens and planetary images get extra points ūüôā
  2. How much did Luke travel in all?
  3. How much did Luke travel North? West?

Luke traveled a ‘distance‘ of 15 Kms in all. In the direction of North he only traveled 10 Kms. So the ‘displacement‘ is 10 Kms North. Similarly, his ‘displacement‘ west is 5 Kms.

Here is the picture from Star Wars on the two suns setting in the planet of Tatooine.


A shot of Luke Skywalker and his pod.


As the text book definition [2] goes:

Distance and displacement are two quantities that may seem to mean the same thing yet have distinctly different definitions and meanings.

  • Distance is a scalar quantity that refers to “how much ground an object has covered” during its motion.
  • Displacement is a vector quantity that refers to “how far out of place an object is“; it is the object’s overall change in position.

Displacement has a value and direction (called vector in physics). Distance just has value (called scalar). As we go along we will see why the distinction is needed.


  1. Introduction to displacement, velocity and time in Khan Academy
  2. 1-D kinematics: Distance and displacement from PhysicsClassroom
  3. Tatooine pics
  4. Luke and his pod

Absolutely nothing about the bird


You can know the name of a bird in all the languages of the world, but when you’re finished, you’ll know absolutely nothing whatever about the bird… So let’s look at the bird and see what it’s doing — that’s what counts” – Richard Feynman

Meeting interesting people 

Path to excellence is about finding your passion and expressing yourself in a voice that is your own. Meeting interesting people who do that can be a great way to (un) teach children how to do that. But, life of a middle class family is pretty predictable. Most people make safe choices out of fear than love or passion.


The social network around a middle class family is very homogeneous. You encounter a very predictable class of people. So how do your break out of that band and get your kids to meet interesting people?

I think the online world comes to the rescue here. I recommend the following shows that give us a peak into the world of interesting people. You can watch them and introspect on the takeaways from the stories. I always ask them to synthesize back the human thinking behind the stories. Why did he/she do what they did. The struggles. The choices.

Emphasize the choices and what it takes to live with those.

  1. Chef’s Table on Netflix
  2. Abstract on Netflix
  3. Love of Physics – Lectures for kids by Walter Lewin

Start unfocused 

I often try to carve out a time for my kids to learn and for me to teach on the weekend. I go in all excited and focused.

I am often faced with a lot of ‘avoiding’ ¬†techniques.Looks of distraction/boredom, bouts of silly laughter, hunger pangs, extreme body itching or rubbery spine.

I started getting irritated and pushed for greater focus. How can they not see the plans I am making?? That always lead to bouts of crying or complaining.

I then tried a very different tack. Go with the flow. Crack a joke  or two. Defuse the situation.  Then slowly nudge the conversation towards the current topic. Tell stories. Arouse curiosity. Create a sense of intrigue.

Let them ease into it. Don’t force ¬†it. Kids don’t turn on immediately. The insight was to let them be. Let them be playful. That’s what kids do. Play.

Let’s start unfocused. Focus follows curiosity and fun for kids. May be for everyone!!

When your kid calculates Pl …¬†

I talked to my son about how magical Pl is. How it appears in so many places in nature. It was observed. Ancients measured the circumference of the circle and it’s ratio with the diameter. That remained constant irrespective of the circle – PI. It also shows up in so many places in Physics.

How many people tried calculating PI including 5th century mathematicians in China / India, Archimedes and Srinivasa Ramanujam. We talked about how hard it is to calculate PI. How it is an irrational number and no repeatable patter. Then I said we will beat Archimedes today…¬† in one afternoon.¬†

Swiss army knife isolated

Creating a sense of mystery and adventure I feel is key to getting kids excited about learning any thing new. They always want to play. Why not? 


Then we talked about the intuition behind the Archimedes method [1]. If your draw a polygon-and-circlespolygon (multi-sided shape like a square with 4 sides) in a circle and then keep increasing the number of sides, eventually it will come very close to a circle. Archimedes had a simple way to calculate the perimeter of the polygon and thus approximate the circumference of the circle.

Archimedes stopped at a 96 sided polygon. Using simple excel or a more sophisticated program in python we can go to MNs of sides to estimate the perimeter easily.

The interesting thing about using the Archimedes method is that it requires application of Pythagoras theorem, infinite series and basic geometry.

Swiss army knife isolated

Learning happens in the mind of the kid. Only when they reconstruct pieces and learn to assemble seemingly unconnected pieces (Pythagoras theorem interacting with infinite series) will real learning happen. This is the essence of Constructionism.


  1. Calculating PI like Archimedes did

Why programming is not just about programming computers…¬†

Kids should be taught programming. But not with the purpose of writing computer programs. 

Instead they should learn programming to develop a new way of thinking – concepts such as iterations,  use of variables,  reusable blocks,  error handling to refine the solution. To give them a powerful tool to simulate real life and refine their mental models. To allow them to visualize outputs in interesting ways than just drab equations. 

Can we unteach physics or math or biology or even languages thru programming? 

Does programming offer a safe and a low cost way to fail in the journey of solving a problem? 

Will programming develop abstraction of ideas and their implementation?