Quick Theory Recap

Physics in railway exams is limited to 10th-class level, so master the triad of Mechanics–Heat–Electricity.
Start with Scalars vs Vectors (distance, displacement, speed, velocity, acceleration). Newton’s three laws appear every year—remember F = ma is valid only in inertial frames. Friction questions often trick you by switching between static (μsN) and kinetic (μkN) coefficients; the static one is always larger. For circular motion, the centripetal force is not a new force—it is the net force pointing to the centre (tension, gravity, normal or friction). Railway tracks are banked so that N sinθ provides the required centripetal force, reducing wear on the outer rail.

Heat is 30 % of the physics pie. Calorimetry (Q = mcΔθ) and latent heat (Q = mL) are favourite calculation traps—watch the units (kcal vs J). Linear expansion of rail lines (ΔL = αLΔT) is asked almost every year; a 20 °C summer rise can buckle a 20 m steel rail by ~5 mm. In electricity, Ohm’s law (V = IR) and power formulas (P = VI = I²R = V²/R) are the golden trio. Remember: for the human body the safe current is < 1 mA, and the fuse wire must have high resistance & low melting point. Magnetic effect of current gives the Right-hand thumb rule for straight wires and Fleming’s Left-hand rule for motors—railway fans, traction motors work on this principle. Finally, mirror & lens sign convention: “Real is positive, virtual is negative”—stick to Cartesian convention and 90 % ray diagram problems collapse to a single formula: 1/v – 1/u = 1/f.

Practice MCQs

1. Which of the following is a vector quantity?
   A. Speed
   B. Distance
   C. Velocity
   D. Mass

2. The slope of a velocity-time graph gives:
   A. Displacement
   B. Acceleration
   C. Momentum
   D. Force

3. A 2 kg stone is dropped from rest. After 2 s its momentum is (g = 10 m/s²):
   A. 10 kg·m/s
   B. 20 kg·m/s
   C. 40 kg·m/s
   D. 0 kg·m/s

4. The work done by friction is always:
   A. Positive
   B. Negative
   C. Zero
   D. May be positive or negative

5. A train moving at 72 km/h stops in 50 m. Retardation is about:
   A. 1 m/s²
   B. 2 m/s²
   C. 4 m/s²
   D. 0.5 m/s²

6. Two 5 Ω resistors in parallel give equivalent resistance:
   A. 2.5 Ω
   B. 5 Ω
   C. 10 Ω
   D. 25 Ω

7. The unit of electric power is:
   A. Joule
   B. Watt
   C. Coulomb
   D. Volt

8. A convex mirror always forms an image that is:
   A. Real & inverted
   B. Virtual & inverted
   C. Virtual & erect
   D. Real & erect

9. The specific heat of water is approximately:
   A. 1 J/kg°C
   B. 4200 J/kg°C
   C. 840 J/kg°C
   D. 2100 J/kg°C

10. A 60 W, 220 V bulb has filament resistance of:
    A. 484 Ω
    B. 806 Ω
    C. 220 Ω
    D. 60 Ω

11. When a train blows whistle while approaching a station, the apparent frequency to a listener on the platform:
    A. Increases
    B. Decreases
    C. Remains same
    D. Becomes zero

12. The magnetic field inside a long straight current-carrying solenoid is:
    A. Zero
    B. Uniform & parallel to axis
    C. Non-uniform
    D. Radial

13. A 2 cm tall object is placed 15 cm from a concave mirror of f = 10 cm. Image distance is:
    A. 30 cm
    B. –30 cm
    C. 6 cm
    D. –6 cm

14. Which phenomenon explains the red appearance of the Sun at sunset?
    A. Reflection
    B. Refraction
    C. Scattering
    D. Dispersion

15. A 1 kW heater is used for 5 min. Energy consumed is:
    A. 5 kWh
    B. 0.083 kWh
    C. 12 kWh
    D. 300 kWh

16. If the distance between two charges is halved, the electrostatic force becomes:
    A. Half
    B. Double
    C. Four times
    D. One-fourth

17. The acceleration due to gravity on a planet of double radius & same density as Earth is:
    A. g
    B. 2g
    C. 4g
    D. g/2

18. A 50 cm metre bridge is balanced at 30 cm from left end when R = 2 Ω is on left. Unknown resistance is:
    A. 1.33 Ω
    B. 3 Ω
    C. 1.5 Ω
    D. 0.75 Ω

19. A convex lens behaves as a converging lens in air but as a diverging lens in a liquid of refractive index greater than that of lens material. This is because:
    A. Focal length becomes infinite
    B. Relative refractive index < 1
    C. Lens becomes concave
    D. Snell’s law fails

20. A 200 m long train crosses a pole in 10 s. Time to cross a 300 m platform is:
    A. 10 s
    B. 15 s
    C. 25 s
    D. 30 s

21. Two projectiles are thrown with same speed, one at 30° and another at 60° to the horizontal. Their ranges are related as:
    A. R₁ = R₂
    B. R₁ = 2R₂
    C. R₁ = R₂/2
    D. R₁ = √3 R₂

22. A Carnot engine working between 27 °C and 127 °C has efficiency:
    A. 25 %
    B. 50 %
    C. 75 %
    D. 100 %

23. The colour of light which travels fastest in glass is:
    A. Red
    B. Violet
    C. Yellow
    D. Blue

24. A transformer has 100 primary turns and 50 secondary turns. With 200 V input, output voltage is:
    A. 400 V
    B. 100 V
    C. 200 V
    D. 50 V

25. A satellite in circular orbit of radius R has time period T. If radius becomes 4R, new period is:
    A. T
    B. 2T
    C. 4T
    D. 8T

Railway-Last-Minute Shortcuts

• Units → write every answer with units; 1 mark is lost for “10” instead of “10 m/s”.
• Power trio → P = VI = I²R = V²/R—memorise the triangle.
• Mirror sign → “UVF”: U (object) always negative for real object, V & F decide real/virtual.
• Train speed → km/h to m/s → multiply by 5/18 in one step.
• Free-fall → 1 s → 10 m/s, 2 s → 20 m/s, 3 s → 30 m/s (g ≈ 10).
• Efficiency → never forget to convert °C → K for Carnot.
• Bridge balance → write 100 – l immediately to avoid silly subtraction error.
• Options → if two choices differ by 5/18 or 1/2, recheck units—railway exam loves unit traps.

All the best—keep the force with you!