Quick Revision ⚡
Last-hour exam preparation. Formula dump, flashcards, memory tricks, and one-line summaries. Scan in 15 minutes before you walk into the exam hall.
📐 Formula Dump
Every formula you need. One glance. No explanations needed at this point.
WORK DONE
KINETIC ENERGY
POTENTIAL ENERGY
POWER
SPECIAL RESULTS
🃏 Flashcards
Click card to flip. Use ← → to navigate. Test yourself.
Work done by centripetal force?
F ⊥ v always in circular motion → cos 90° = 0
⚡ One-Line Summaries
Core physics in one sentence. Read aloud for maximum retention.
🧠 Memory Tricks
Mnemonics, patterns, and shortcuts that stick.
"W-K-P-E" = Work-KE-Power-Energy
Remember the main quantities in order of complexity. W is basic. KE = ½mv². P = W/t. E = KE + PE = constant (no friction).
"Spring PE is a Parabola" — PE = ½kx²
The U-shape of PE vs displacement graph IS the parabola y = ½kx². The minimum is at x = 0 (natural length). Beyond this is simple intuition.
"5, 3, 1" for vertical loop
v_bottom : v_middle : v_top in ratio √5 : √3 : 1 (for minimum condition). Speeds are √(5gR), √(3gR), √(gR).
Energy = kg·m²/s² — everything including torque
Memorize [ML²T⁻²] as the "energy dimension." If a formula gives this dimension, it's an energy. Torque also has this dimension — but it's NOT energy. Context matters.
"Heavier-more-momentum" (same KE)
p = √(2mKE). For same KE → p ∝ √m. Heavy = more p. Think of a truck vs a car at same speed squared — truck has more "oomph."
cos values: 0, 0.5, 1/√2, √3/2, 1
For angles 90°, 60°, 45°, 30°, 0° respectively. These cover 95% of NEET work problems. Memorize this row instantly.
"Spring sees force — string sees length"
Series springs: divide force equally (same tension). Parallel springs: share the extension (same displacement). This determines which formula to use for effective spring constant.
"Constant speed → balanced forces → P = friction × speed"
At constant velocity: engine force = total resistive force. Power = resistive force × velocity. Simple, direct, no memorization needed.
❌ Common Traps — Never Fall Again
These mistakes cause 30–40% of marks lost in WEP. Memorize the correct version.
Trap 1: W = ½k(Δx)² for spring increment.
Correct: W = ½k(x₂² − x₁²). The difference of squares, not square of difference.
Trap 2: Friction force on incline = μmg.
Correct: Friction = μN = μmg cosα. Normal force on incline is reduced.
Trap 3: Work done by gravity depends on path.
Correct: Gravity is conservative. Work depends only on vertical displacement (height).
Trap 4: At constant speed, engine does no work.
Correct: Engine works against friction. P = Fv. At constant speed, engine force = friction force.
Trap 5: Spring constant halves when spring is cut in half.
Correct: k ∝ 1/L. Shorter spring → larger k. Half length → double spring constant.
Trap 6: Negative KE can result from friction.
Correct: KE is always ≥ 0. If you get negative KE, you've violated energy conservation — check your friction direction or height calculation.
Trap 7: Both masses reach same speed in elastic collision.
Correct: Only equal masses exchange velocities. Different masses → use the elastic collision formulas.
Trap 8: Static friction always does negative work.
Correct: Static friction can do positive work (e.g., on a book on an accelerating truck — friction drives the book forward).
Final thought: Work, Energy & Power is fundamentally about one principle — energy is conserved and can be tracked. If you understand that principle deeply, the formulas follow logically. You don't need to memorize 30 formulas — you need to understand 3 ideas: (1) W = ∫F·dx, (2) W_net = ΔKE, (3) Conservative forces have PE. Everything else is algebra.