PHY012 · Mechanics · Classes 6–10
Mechanical advantage
Objective: To find the mechanical advantage of a lever and how it depends on the arm lengths.
🧰 Apparatus
- Metre rule as a lever
- Knife-edge fulcrum
- Slotted masses (load)
- Spring balance (effort)
📐 Formulas and SI units
Load × load arm = Effort × effort arm
MA = Load / Effort
💡 Theory
A lever balances when the moments are equal: load × load arm = effort × effort arm. The mechanical advantage MA = load/effort = effort arm / load arm for an ideal lever. A long effort arm lets a small force lift a big load.
🪜 Procedure
- Balance the metre rule on the fulcrum.
- Hang the load at a measured load arm.
- Pull down with the spring balance at the effort arm until balanced.
- Record the effort; repeat for other effort arms.
- Calculate MA and compare with ea/la.
📋 Observations Simulated values
✅ Result and conclusion
A 400 N load at 0.5 m is balanced by 100 N at 2 m: MA = 4.
🔬 In a real lab
The rule's own weight and friction at the pivot change the effort slightly; real levers have MA a little below the ideal.
⚠️ Safety
Lift heavy loads only with a teacher; keep feet clear of hanging masses.
❓ Quick check
1. A seesaw is a lever of class…
2. To lift a load with less effort, make the effort arm…
3. MA of a lever with arms 0.2 m (load) and 1 m (effort)?
🏋️ Practice
EasyLoad 600 N, arms 0.3 m and 1.8 m. Effort?
Answer: 100 N
MediumName a class-2 lever.
Answer: Wheelbarrow, nutcracker
ChallengeName a class-3 lever.
Answer: Tweezers, forearm