Unit 2 • Class 8Science and Technology (Sci.081)
Force and Simple Machines (Three Classes of Levers & Pulleys)
बल र सरल यन्त्रहरू (तीन प्रकारका उत्तोलक र घिर्नी)
Principles of simple machines: Mechanical Advantage (MA = L/E), Velocity Ratio (VR = d_E / d_L), Efficiency (η = MA/VR × 100%), three classes of levers, wheel & axle, inclined plane, and pulley systems.
Lesson Summary & Key Concepts
Mechanics of simple machines: Mechanical Advantage, Velocity Ratio, Efficiency, classification of levers, and inclined planes per Grade 8 BLE specification.
Quick Revision Takeaways
Common Exam Pitfalls to Avoid
⚠️ Common Error: Assuming Velocity Ratio changes when machine parts become rusty or worn.
✓ Correct Approach: VR depends solely on dimensions/geometry and never changes due to friction; only MA and efficiency decrease.
Why: Friction affects forces, not geometric displacements.
Content Provenance & Verification
Editorial Verified & Published
Original Author / ContributorBLE Science Specialist Committee
Verified BySenior Subject Specialist (TU / NEB Panel)
Curriculum Versionv1.0 (CDC 2078/2080 Grid)
Last Verified Date2026-10-23
Legitimate Official Curriculum References
public curriculum
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