Mechanics & Simple Machines · GCSE Physics Moments & Levers
Lever Balance & Torque Moment Arm Simulator
Crucial exam concept: Moment arm is the perpendicular distance from pivot to line of action, NOT pivot to point of application. Tilting reduces arm length and increases required force.
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- Live Derivation
- Projector Mode
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3D Simulation Stage● 60 FPS
Parameter Controls
N
cm
cm
°
Live Derivations & Metrics
Effort Force F1
--
Effective Arm L1
--
Torque M
--
Min Force (at 90°)
--
Real-Time Formula Derivation
Governing Formula:
--Substitution:
--Regime: --
Related Tool:
🔧 Standard Tool: Bolt Torque & Preload Calculator ↗
Worked Examples & Exam Question Deep Dive
Worked Problem
Problem: A 1m lever has pivot at left. A 60N load hangs at 0.4m. Find effort at right end vertically and at 30° upward angle.
Step-by-Step Derivation:
- 1) Vertical: L1=1m, F1 = 60*0.4/1 = 24N. 2) At 30°: L1' = 1*sin30° = 0.5m, F1' = 60*0.4/0.5 = 48N.
Worked Problem
Problem: A uniform 400N log rests on the ground. What upward force is needed to lift one end?
Step-by-Step Derivation:
- Center of gravity is at L/2. Pivoting on ground end gives F1*L = G*(L/2), so F1 = G/2 = 200N.
Student Inquiry Worksheet & Practice Problems
Q1. Variant 1: Which are third-class levers: bottle opener, claw hammer, tweezers, fishing rod, balance scale?
Answer Key: Tweezers and fishing rod. They save distance, allowing small hand motions to produce large tip displacements.
Q2. Variant 2: Why level a laboratory lever horizontally before taking measurements?
Answer Key: 1) Cancels lever weight about pivot; 2) distances along the horizontal ruler directly equal perpendicular moment arms.
Q3. Variant 3: A 1.2m pole carries 300N at one end and 200N at the other. Where should the shoulder support it?
Answer Key: Let distance to 300N be x: 300*x = 200*(1.2 - x) => 500x = 240 => x = 0.48m from the 300N bucket.
Frequently Asked Questions & Misconceptions
Can a moment arm be zero?
Yes. If the line of action passes directly through the pivot, perpendicular distance L=0 and torque is zero, causing no rotation.
Why does tilt angle increase spring balance reading?
Because load torque F2*L2 is constant. Tilting reduces effort arm L1 = d*sinθ. To maintain equilibrium, effort F1 must increase inversely.
What class of lever is a balance scale?
It is an equal-arm lever (L1 = L2). Because arms are equal, equilibrium occurs when forces match, measuring mass directly without mechanical advantage.
Can a force-multiplying lever save work?
No. While effort is smaller (F1 < F2), effort displacement is proportionally larger (s1 > s2). Conservation of energy dictates F1*s1 ≥ F2*s2.