# June 7, 2016: Force Foundations – Carousels & Gears

Ladymaker Allison Berman taught moms and daughters about physics and engineering with an introduction to simple machines. Moms and daughters first learned how machines such as levers can be used to turn a little force into a big one. A seesaw, for example, is just a lever that changes the direction and amount (magnitude) of force. The lever has a pivot point called a fulcrum, the point at which work changes from input to output. While work (force over distance) must be equal on both sides, the distance and amount of force on each side can change. This means that a tiny force over a big distance can equal the work of a big force over a short distance. If a child weighs half that of her parent, she still can lift her parent high in the air by sitting twice the distance from the fulcrum as her parent.

Levers can be found everywhere. Even joints in our bodies are levers. Joints help us move by enabling us to use a tiny force from muscles and tendons to move our limbs. Bicycles combine machines all in the lever class; wheels, gears, and pulleys all are levers that rotate. If we picture the gears on a bicycle and the size of the wheels, we see that the wheels are always bigger than the gears. If we move our legs a small amount with a lot of force, it moves the wheels a much larger amount and we cover more distance than if we were walking.

After discussing the workings of simple machines all around us, moms and daughters began to experiment with force and motion with carousel boards and various sizes of wooden gears designed and laser cut by Allison. Girls learned that putting a lot of force on a small gear will slowly turn a larger gear. A large force on a large gear will turn a smaller gear fast. If one gear is three times as big as the other, then for every one turn that big gear makes, the little one will turn three times.

It then was time to put everything together in a carousel. Each team mounted their carousel base and large gear to a board with a 3/16″ wide peg and a metal washer to reduce friction. Girls chose carousel animals and added them to their base gear, then decorated their creations and finished each with a carousel top. The teams then assembled a series of gears on their boards to power their tiny merry-go-rounds with the touch of a finger.

Our Make-HER engineers combined very simple machines to create beautiful take-home carousels. Each carousel was different, as was each series of gears used to create its spinning movement. Best of all, the pieces all come easily apart and are sized to fit LEGO Technics axles for further exploration and play.

At the end of the workshop girls discovered that their gear trains could be joined, resulting in several carousels spinning with just one person turning a single small gear.