The CyberSquad needs to fix the train in order to get up the mountain. They manage to get it moving by putting in a missing gear; however, it travels too slowly. They note that gears of different sizes turn at different speeds and that a gear with a high number of teeth will make the train move fast when paired with a gear with few teeth. They swap out a couple of gears and get the train moving at a fast rate.

Bill Nye show us how a circuit works by comparing electrons to water.

Mr. Seaver begins teaching the class a lesson on gravity out of the textbook. He is especially confused by the book's claim that a coin and a feather will fall at exactly the same speed. After Luke challenges him to prove it, he tests the claim.

A series of simple machines help collect mushrooms and crush them to produce a drink for Dr. Robotnik.

The students and Ms. Frizzle travel to Mercury, the first planet in our solar system, and learn that they weigh less because there is less gravity on the planet. They enjoy bouncing around with less gravity, and a few students take part in a contest to see who can jump higher.