Lesson 3: String, Levers, and Axles
Duration of Days: 6.5
Lesson Objective
Students will calculate the mechanical advantage of their drive system and determine the ideal lever-arm-to-axle ratio.
1. Why does a thin axle provide more "starts" but less "pull"?
2. How does string tension affect the initial "snap" of the car?
Mechanical Advantage, Tangential Force, Circumference, RPM.
ENG.06.01: Use appropriate math and science concepts to solve engineering problems
Students attach their lever arm and string. They will experiment with "winding" the string—testing how the diameter of the axle (using tape to "fatten" it) changes the acceleration.
Purpose: To optimize the energy release for either a "drag race" (speed) or "marathon" (distance).
DOK Level: Level 3 (Strategic Thinking).
Create "Success Groups" where students specializing in "Speed" work together to compare gear ratios (axle diameters).
Mathematical calculation of the car's theoretical travel distance based on string length and wheel circumference.
High-test fishing line or upholstery thread, masking tape (to adjust axle diameter), various wheel types (CDs, records, plastic wheels).