STEM Labs
Changing Velocity

Teacher Portal

Answer the following questions in your engineering notebook after completing the activities.

• In Protect the Castle!, did the robot turn in a perfect square? What might be the reason why the robot did not move and turn the exact distances written in the project?

• In Robot Waiter, the turn velocity could be set higher than the drive velocity. Why do you think that was true

Teacher Toolbox - Answers

• No, the Autopilot did not move in a perfect square because its turns were not perfectly 90 degrees, or its drive distances were not exactly as programmed. The robot may not always move the exact value written in the code. Here are some possible reasons why:

• Variations of Friction

• If the surface is very smooth, the Autopilot’s wheels may spin the amount of rotations it was programmed, but not travel as far as it should. This is similar to a car wheel on an icy surface.

• If the Autopilot is running on a plush carpet, the carpet may interfere with the tire rotation.

• Dirt and/or dust on the wheels may also cause a loss of traction.

• Momentum

• If the Autopilot traveling has enough momentum, it may coast slightly from that force, even though the motors have completed their designated rotations.

• Improper Build

• Wheels are not completely connected to the wheel axis and frame.

• The Autopilot may not be balanced due to its construction, materials, weight, or axis of rotation not being symmetrical. This can cause it to move forward or in reverse incorrectly.

• Students might have many different speculations. Here are the better possibilities:

• The turning of the shape of the pitch standoff is rounded but long. So it can only roll forward and backward when positioned across the VEX IQ decal on the brain. The drive blocks but not the turn blocks risk making it roll forward and backward on the brain.

• The position of the brain in the middle of the build also makes it less influenced by spinning than positions toward the outside of the build.