Event Overview
Teams take a written test on simple and compound machine concepts (levers, pulleys, inclined planes, mechanical advantage, efficiency), and also pre-build a lever-based measuring device to determine the mass ratios of three unknown test masses at competition.
π Hybrid: written test component plus a pre-built lever/balance device used at competition for measurement tasks
π Study Guide
Machines
Category: Physical Science & Chemistry
Format: Hybrid (Test + Built Device)
2026 Topic: Simple & Compound Machines
Participants: 2
What It Is
Machines is a hybrid event combining a written test on simple and compound machine theory with a built-device component. Teams pre-build a lever-based measuring device and use it at competition to determine the mass ratios of three unknown test masses. The event tests both conceptual physics knowledge and precision engineering.
What to Know
Simple Machines:
- Six simple machines: lever, wheel and axle, pulley, inclined plane, wedge, screw
- Mechanical advantage (MA): ideal MA vs. actual MA, efficiency
- Force Γ distance = work; conservation of energy in ideal machines
- Lever classes (1st, 2nd, 3rd class): fulcrum/effort/load positions, examples
- Pulley systems: fixed, movable, block and tackle; MA = number of rope segments supporting load
- Inclined plane: MA = length/height; wedge and screw as inclined planes
Compound Machines:
- How simple machines combine: overall MA is product of individual MAs
- Real-world examples: scissors, wheelbarrow, bicycle, cranes
- Efficiency losses: friction, deformation; calculating actual MA and efficiency
Lever-Based Measuring Device:
- Torque: Ο = F Γ r; rotational equilibrium (Ξ£Ο = 0)
- Using torque balance to measure unknown masses: ratio method
- Calibration: establishing reference masses and positions
- Precision of the lever device: minimizing friction at fulcrum, beam rigidity, reading position accurately
- Sources of error: fulcrum friction, beam non-uniformity, parallax in reading position
Competition Format
Written test component covers simple and compound machine theory (multiple choice, short answer, calculations). Device component: teams use their pre-built lever device to determine the mass ratios of three provided unknown masses. Both components contribute to the final score.
Notes
- Lever device must be pre-built; no modifications allowed at competition.
- Torque-balance calculations are the core skill: practice solving Οβ = Οβ equations quickly.
- Device precision depends heavily on a smooth, low-friction fulcrum β this is a key design element.
- Read the event rules carefully for device size/mass restrictions.