STEM Labs
Changing Velocity

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• The Purpose of this Section
The goal of the Play section is for students to learn to program the Autopilot robot to drive and turn at different velocities by using the [set drive velocity] and [set turn velocity] blocks. The students begin the Play section by learning to drive at the default velocity (50%), decrease, and then increase the velocity. Before beginning the activity, they add a pin to one of the Autopilot’s wheels so that they can more clearly see the differences in the velocity. Next, they learn to turn at the default velocity (50%), decrease, and increase the velocity.

Read this page with students before moving on to the Changing Velocity exploration. Use the Motivate Discussion questions after the reading to consider when they might change the velocity of their robots for different tasks.

• Robot Behaviors
For Robot Behaviors for Changing Velocity, click one of these links (Google Doc/.docx/.pdf).

VEX IQ Smart Motors can be programmed to spin or drive at many different velocities. If you have programmed your robot to drive or turn before, you probably did it with the default velocity. The default velocity is the velocity that the Smart Motors turn at automatically - if you don’t add any type of block for setting the velocity. The default velocity is 50% of the maximum velocity. The maximum velocity is 100%.

The blocks for setting velocity are important because you might want your robot to drive or turn faster or slower. For example, you might be racing against another robot and want your robot to drive as fast as possible. Or, you might want your robot to drive or turn more slowly like when it has to carefully complete a task like moving through a maze.

Motivate Discussion

Q: Has any student used a block to set velocity before? Why did they use it? How did it make their robot’s project better?
A: If no student has used one before, you can move on to the next question. If a student(s) has used one, ask them to explain why they used it in their project. Highlight for all students that slowing the motors down or increasing them was appropriate for the robot’s task.

Q: What things would you program a robot to do slowly? What things would you program a robot to do quickly?
A: Answers could vary greatly but this discussion should highlight that tasks requiring careful precision are often completed more slowly. In situations when time-to-completion is more important than careful precision, the robot could be programmed for faster movements.

Teacher Toolbox - Speed vs. Velocity

This STEM Lab has students use blocks for setting the velocity but primarily focuses on changing the percentage of the maximum speed within the velocity block. Velocity is typically defined as both speed and direction. Students might ask about this. Changing the speed of the robot also changes it velocity. The direction of the robot’s movement is set in other blocks (e.g., a [drive] or [turn] block).