Quick-Revision Physics One-Liners
RRB NTPC / Group-D / JE – Last-Day Sheet
⚙️ Mechanics – Force & Motion
- 1st Law: Body lazy to move → “MR. INERTIA” (M=Mass, R=Rest)
- 2nd Law: F = ma → “F=Ma’am” (say it fast)
- 3rd Law: Action = –Reaction → “Every slap has a equal-pain slap back”
- Momentum: p = mv (p like “power-ride”)
- Impulse: J = F·Δt = Δp (J=Jump in momentum)
| Use & Throw | Formula | Unit | Trick |
|---|
| Acceleration | a = Δv / Δt | m/s² | “a-v-t” alphabet order |
| Centripetal | F = mv²/r | N | “V-square ride on radius” |
| Kinetic energy | KE = ½mv² | J | “Half-movie” |
⚡ Electricity – 5-Minute Capsule
- Ohm’s Law: V = IR → “Victory Is Rare”
- Power trio: P = VI = I²R = V²/R (VIP-R)
- Series: R↑ like “Resistors in line—length ↑→R↑”
- Parallel: 1/R↓ like “Many paths—traffic ↓→R↓”
- Joule heat: H = I²Rt (H=I-square Right)
| Quantity | Symbol | SI Unit | Remember |
|---|
| Charge | q | Coulomb | “q=Couple” |
| Current | I | Ampere | “I-Am” |
| Resistance | R | Ohm (Ω) | “Oh-Mega” |
🔋 Magnetism & EMI
- Fleming’s LH rule (Motor) → “Motor needs Left-hand Power”
- Fleming’s RH rule (Gen) → “Right gives Revenue (current)”
- Lenz Law: “Opposes the cause” → Like “lazy kid pushes back work”
- Transformer: Vs/Vp = Ns/Np = Ip/Is (step-up ↑V ↓I)
☀️ Light – Mirror & Lens
- Mirror formula: 1/f = 1/v + 1/u (sign convention: “UV-light” u & v)
- Lens power: P(D) = 1/f(m) → “Power is inverse of focus”
- Speed of light: 3 × 10⁸ m/s → “Three-eight-straight”
| Real Image | Virtual Image | Trick |
|---|
| Can catch on screen | Can’t catch | “Real-screen, Virtual-dream” |
| Inverted | Erect | “Real is rude (inverted)” |
🌡️ Heat & Thermo
- 0th Law: “Thermo-Handshake” – If A=B & B=C ⇒ A=C
- 1st Law: ΔU = Q – W (Work by system) → “You-Q-W”
- Cp – Cv = R (for ideal gas) → “Cp minus Cv is Railway (R)”
- Black body: ε = 1 perfect radiator → “Black=1, White=0”
📡 Sound – Rapid Fire
- Speed in air: 332 m/s @0 °C → “332-Zero”
- Echo: 2d = v·t → minimum 0.1 s ⇒ 17 m distance
- Pitch ∝ frequency, Loudness ∝ (Amplitude)²
🚀 Modern Physics – 3-Finger Rule
- E = hf (Photon energy) → “E-hugs-frequency”
- 1 eV = 1.6×10⁻¹⁹ J → “Electron-volt is one-sixteen”
- α-particle: 2p+2n → “Alpha-double-date”
- β-particle: fast e⁻ → “Beta-beat-electron”
- γ-ray: EM wave → “Gamma-gift-light”
🛠 Units & Dimensions – Cheat Table
| Physical Qty | Unit | Dimension | Quick |
|---|
| Force | N (kg·m/s²) | MLT⁻² | “F=Ma” |
| Energy | J (N·m) | ML²T⁻² | “Joule=Force-dot-meter” |
| Power | W (J/s) | ML²T⁻³ | “Watt=Joule-per-sec” |
✨ Exam-Trap Shortcuts
- Weight ≠ Mass → Weight = mg (changes on Moon)
- AC vs DC – “AC-Alternates, DC-Direct chalan”
- Bulbs in series: if one fuses, all off (like “rail-chain”)
- Fuse wire: low melting, high R → “Fuse-First-Sacrifice”
🔁 Quick Q&A (One-liner answers)
Q1. On doubling speed, KE becomes?
4 times (KE ∝ v²)Q2. Device to measure potential difference?
VoltmeterQ3. Colour of light with max wavelength in VIBGYOR?
RedQ4. Unit of magnetic flux?
Weber (Wb)Q5. Sound can’t travel in which medium?
Vacuum
🎯 Last 60-Second Glance
- g = 9.8 m/s² → “Nine-fine-eight”
- 1 hp = 746 W → “Seven-four-six, horse-power mix”
- Refractive index: μ = c/v > 1 always → “Mu-see-vee, always above sea”
Revise → Sleep → Crack it!
BETA
