Steve Jobs speaks to the Macintosh team about the importance of user-centered design.

In this example of poor user experience design, the government has designed two identical buttons: one launches all of the country's nukes, and the other makes coffee. The takeaway is that the look of a feature should match its importance and urgency. A button that launches the nukes should probably be small, round, and not very easy to access, whereas a button to make coffee could be larger and in a more accessible place.

The Rocket Boys run several tests in order to perfect their rocket design. They use the launch results as feedback to help them refine their design.

Beakman explains how gas is explosive and causes the combustion engine in the car to work. He uses a model engine with a side view and demonstrates what is happening with the gasoline when it explodes to move the engine parts. Beakman shows how the engine allows the wheels to turn by relating it to riding a bike. Up and down motion of the pedals is converted to turning the wheels through the chain. Same in the car with the pistons turning gears and thus the wheels.

Beakman explains what a submarine is and how buoyancy and density affect a submarine rising and sinking. Then he makes a DIY submarine from a soda bottle.