# Island 2 K'nex Motors

Get To Know Gears, Ratios And Motors

Students will expand their knowledge of simple machines. Learn about force, work, gear ratios and mechanical advantage. Build gear systems and machines that use gear systems and explore how they help us do difficult jobs.

## K'nex Motors

Study Of Dynamics

Mechanics is the area of physics concerned with the effect of forces on physical bodies.

Mechanics is divided into various areas including statics, which is the study of structural systems that do not move, and dynamics, which is the study of bodies in motion.

Dynamics includes everything from kicking a rock, swinging a baseball bat, and a spinning pinwheel, to a crane lifting a massive weight, a rocket launching into space, and even the entire Earth moving around the sun.

In this Learning Launcher, students will focus on dynamics of gear systems. Gears are simple machines heavily based on motion. They help redirect force and motion by changing rotational speeds and rotational directions to fit our needs.

Gears

Just like the lever, gears allow us to increase the distance traveled so we can perform work with less force. Instead of linear distance, however, it refers to circular distance based on how large a gear's circumference is.

Gears can create a mechanical advantage by using different size gears with different circumferences. If one gear is wider than another connected gear, they may have the same rotational speed, but the outer edge of the larger gear still has to cover more distance than the smaller gear in order to complete a full rotation. In other words, the larger gear's teeth move slower around the circle than those of the smaller gear.

By increasing the size of a gear, it also causes the gear to produce more rotational force or torque.

This is the basis for how gear trains trade rotational speed for force. Smaller gears have faster-moving teeth but produce less torque, while larger gears have slower-moving teeth but can produce more torque.