Lesson 2: Stability and the Righting Moment
Duration of Days: 5
Lesson Objective
Students will strategically place floats and weights to ensure the ROV is "self-righting" and stable along its roll and pitch axes.
Why should the "heaviest" parts be at the bottom and the "lightest" parts at the top?
What is the difference between being "balanced" and being "stable"?
How does the placement of the tether affect the ROV’s "level" in the water?
Metacentric Height: The measurement of the initial static stability of a floating body.
Righting Moment: A force that returns a body to its original position after it has been tilted.
Pitch and Roll: The forward/backward and side-to-side tilting of the ROV.
Self-Righting: A design feature that ensures the ROV returns to an upright position automatically.
NGSS HS-PS2-2: Use mathematical representations to support the claim that the total momentum of a system of objects is conserved (stability of forces).
Description: Students refine their float and weight placement. They will purposefully flip their ROV upside down in the tank to observe if it "rights" itself. They will also test the "Pitch" to ensure the ROV stays level when moving forward.
Purpose: To ensure the ROV is pilot-friendly. A robot that is neutrally buoyant but unstable (constantly flipping) is impossible to navigate.
DOK Level: Level 4 (Extended Thinking). Students must synthesize their understanding of the Center of Gravity and Center of Buoyancy. They are evaluating a complex system where moving a weight 1 inch can have a massive impact on performance.
In this course, we recognize that students enter the lab with varying levels of technical experience. Our differentiation strategy employs a 'Scaffolded Autonomy' approach. We provide structured, step-by-step guidance for foundational concepts while offering open-ended, 'Design Challenge' extensions for advanced learners. By utilizing peer-mentorship models, diverse instructional media (visual, tactile, and digital), and flexible project pathways, we ensure every student can move from consumer to creator at their own pace.
The "Tumble Test": The teacher flips the ROV 180 degrees underwater. The ROV must automatically rotate back to its upright, level position within 3 seconds without motor intervention.