Physics Formulas

⚡ Quick-Revision: Physics Formulas for Railway Exams


🔥 Mechanics
QuantityFormulaMnemonic
ForceF = ma“F=Ma” sounds like “Effort = Move it!”
Momentump = mv“p” for push
WorkW = F·s·cosθWork = Force slides
PowerP = W/tPower is Work time
Kinetic EnergyKE = ½mv²“Half-em-vee-square”
Potential EnergyPE = mgh“Em-G-H” = Mountain-Gravity-Height

🌊 Fluids & Thermo
  • Density: ρ = m/V → “Rho = Mass per Volume”
  • Pressure: P = F/A → “Press = Force over Area”
  • Buoyant Force: F = ρgV → “Rho-g-V lifts you up”
  • Ideal Gas: PV = nRT → PeVe NeRaTa (Hindi: Pee-Vee-Nerat)
  • Heat: Q = mcΔT → “Q = mc-Delta-T” like McDonald’s ΔT burger

Electricity & Magnetism
NameFormulaTrick
Ohm’s LawV = IRVery Impolite Rascal”
Power (elec)P = VI = I²R = V²/RPlay Virtual India”
Resistance (series)R_eq = R₁ + R₂ + …“Sum up”
Resistance (parallel)1/R_eq = 1/R₁ + 1/R₂“Flip & add”
Force on chargeF = qvB sinθFast queen van Bends”

🌌 Waves & Light
  • Wave speed: v = fλ → “Very fast λambda”
  • Lens formula: 1/f = 1/v + 1/u → “Friend Visits U
  • Refractive index: n = c/v → “n is c over v
  • Snell’s Law: n₁sinθ₁ = n₂sinθ₂ → “N1-S1 = N2-S2

🚀 Motion in 1-D
  • v = u + at
  • s = ut + ½at²
  • v² = u² + 2as
  • Mnemonic: “Unique Attitude Takes Success”

🧲 Magnetic Field
  • Straight wire: B = μ₀I/(2πr) → “Mu-Zero-I-over-2-Pi-r
  • Solenoid: B = μ₀nI → “n turns give Boost”

🎯 10 Rapid-Fire MCQs
1. A 2 kg mass accelerates at 4 m/s². Force is?**Ans:** 8 N (F = ma = 2×4)
2. Power = 100 W, time = 5 s. Work done?**Ans:** 500 J (W = P×t)
3. KE of 4 kg mass at 10 m/s?**Ans:** 200 J (½×4×10²)
4. 3 resistors 2 Ω each in series. R_eq?**Ans:** 6 Ω
5. Same 3 resistors in parallel. R_eq?**Ans:** 2/3 Ω
6. Frequency 50 Hz, λ = 4 m. Wave speed?**Ans:** 200 m/s (v = fλ)
7. A lens has f = 20 cm, u = 30 cm. v is?**Ans:** 60 cm (1/v = 1/f – 1/u)
8. Q = 2 kg copper, c = 0.4 J/g°C, ΔT = 50°C. Q in kJ?**Ans:** 40 kJ (Q = mcΔT = 2000×0.4×50)
9. Current 2 A, resistance 5 Ω. Power?**Ans:** 20 W (P = I²R)
10. A body falls freely from rest for 5 s (g = 10 m/s²). Distance?**Ans:** 125 m (s = ½gt²)

Last-minute tip: Write formulas on 3×3 sticky notes—stick on your mirror; glance twice daily → Retained till exam day!