# Unit 2 - Gear Ratios and Drive Trains

## Unit Objectives

This unit teaches students about the various gears available in a VEX robotics kit. They will understand how to calculate a gear reduction and how to apply these calculations to manipulate the speed of their robot.

## Unit Teacher Notes

### Lesson 2.1 (60 minutes)

This lesson will teach students about gears and the trade off between speed and torque as it relates to drivetrains.

#### Outcomes

• Identify the different types of gears
• Explain the difference between speed, power and torque and vary the gear ratio (and the mechanical advantage) in a system, which gives them the versatility necessary to accomplish whatever work needs to be done.
• Demonstrate the correct use of the calculations needed to choose a gear reduction for either high speed or low speed.

### Lesson 2.2 (60 minutes)

Students will apply their newfound knowledge of gear reduction to calculate the distance that a robot travels based on the input speed of the robot and the wheel size.

#### Outcomes

• Describe the relationship between radius, diameter, circumference, revolutions and distance for a wheels

### Lesson 2.3 (420 minutes)

Students will apply their newfound knowledge of gear reduction to calculate the distance that a robot travels based on the output speed of the robot based on different gear reductions.

#### Outcomes

• Analyze the features of their robot and identify/synthesize how to change them to get different results for high speed or low speed
• Graph the results of their experiment in a meaningful way and discuss situations where the results did not follow the expectation.

### Quiz (30-60 minutes)

Quiz on the unit

#### Outcomes

• Check for Understanding