Activity

## Finding Speed with Finch II

Measure how far the Finch goes in a predetermined amount of time and graph the data to calculate its speed.

## BEGINNER: Outputs Only

Required Lessons: Controlling Wheels, Pen Mount and Plastic Brick Adapter

When you use the Finch Wheels blocks, you set the speed of the motors as a percentage, such as 50%. More commonly, we express speed as a rate of distance per unit time. In this activity, you will measure how far the Finch moves as you vary the speed of the motors and the time the Finch moves. Then you will graph your data and estimate the speed of the Finch in centimeters per second.

Measurement procedure:

1. Place a marker in your Finch.
2. Create a program that uses the Finch Wheels block to move the Finch at 10% speed for 1 s. Both wheels should be set to the same speed so that the Finch moves in a straight line.
3. Run your program. Then pick up the Finch and measure the length of the line it drew in centimeters. Record this data in the first line of the Table below.
4. Repeat this process, changing your program to measure how far the Finch moves for each combination of speed and time in the table below.

Graphing Procedure:

1. Create a plot for the data you took at 10% speed. This plot should show the time in seconds on the x-axis and the distance in centimeters on the y-axis. How does distance vary with time?
2. The proportional relationship between distance in centimeters and the time in seconds represents the speed of the Finch in cm/s. Use your graph to estimate the speed of the Finch in cm/s.
3. Repeat this process to estimate the speed in cm/s when the wheels move at 50% and 90%.
4. How is the Finch’s speed as a percentage related to its speed in cm/s?

Required Lessons: Encoders

When you use the Finch Wheels blocks, you set the speed of the motors as a percentage, such as 50%. More commonly, we express speed as a rate of distance per unit time. In this activity, you will measure how far the Finch moves as you vary the speed of the motors and the time the Finch moves. Then you will graph your data and estimate the speed of the Finch in centimeters per second.

Measurement procedure:

1. Create a program that uses the Finch Wheels block to move the Finch forward. The program should do the following:
• Reset the encoders before the Finch begins moving.
• Move the Finch at 10% speed for 1 second.
• The Finch wheel moves 15.7 cm in one rotation. Calculate the distance traveled in centimeters by multiplying the value of the right encoder by 15.7.
• Display the distance moved by the Finch.
2. Run your program and record the distance moved in the first line of the Table below.
3. Repeat this process, changing your program to measure how far the Finch moves for each combination of speed and time in the table below.

Graphing Procedure:

1. Create a plot for the data you took at 10% speed. This plot should show the time in seconds on the x-axis and the distance in centimeters on the y-axis. How does distance vary with time?
2. The proportional relationship between distance in centimeters and the time in seconds represents the speed of the Finch in cm/s. Use your graph to estimate the speed of the Finch in cm/s.
3. Repeat this process to estimate the speed in cm/s when the wheels move at 50% and 90%.
4. How is the Finch’s speed as a percentage related to its speed in cm/s?

## MATERIALS

Beginner:

• Lay down butcher paper, large poster paper, or similar on the table or floor.
• Use washable markers for easy cleanup.

## INTEGRATION

This activity fits well with middle school math concepts including plotting bivariate data, proportional relationships, and linear equations.