Key Concepts & Formulas

10 Practice MCQs

Q1. A train travels 200 km from Delhi to Agra and returns back to Delhi. What is the displacement of the train? A) 400 km B) 200 km C) 0 km D) 100 km

Answer: C) 0 km

Solution:

• Distance covered = 200 km (Delhi→Agra) + 200 km (Agra→Delhi) = 400 km
• Displacement = Final position - Initial position = Delhi - Delhi = 0 km

Shortcut: Round trip always gives zero displacement

Concept: Physics Basics - Distance vs Displacement

Q2. A Rajdhani Express covers 360 km in 4 hours. What is its average speed? A) 80 km/h B) 90 km/h C) 100 km/h D) 120 km/h

Answer: B) 90 km/h

Solution:

• Speed = Distance/Time = 360 km ÷ 4 hours = 90 km/h

Shortcut: Direct division of distance by time

Concept: Physics Basics - Average Speed

Q3. Which of the following is a vector quantity? A) Mass B) Temperature C) Velocity D) Time

Answer: C) Velocity

Solution:

• Vector quantities have both magnitude and direction
• Velocity has both speed (magnitude) and direction
• Others are scalar quantities (only magnitude)

Concept: Physics Basics - Scalar vs Vector

Q4. A metro train accelerates from 0 to 72 km/h in 20 seconds. What is its acceleration? A) 1 m/s² B) 2 m/s² C) 3.6 m/s² D) 5 m/s²

Answer: A) 1 m/s²

Solution:

• Convert 72 km/h to m/s: 72 × (1000/3600) = 20 m/s
• Using a = (v-u)/t = (20-0)/20 = 1 m/s²

Shortcut: km/h to m/s → divide by 3.6

Concept: Physics Basics - Acceleration

Q5. A 5000 kg goods train is moving at 10 m/s. What is its momentum? A) 500 kg·m/s B) 5000 kg·m/s C) 50000 kg·m/s D) 25000 kg·m/s

Answer: C) 50000 kg·m/s

Solution:

• Momentum p = m×v = 5000 kg × 10 m/s = 50000 kg·m/s

Concept: Physics Basics - Momentum

Q6. A porter lifts a 20 kg suitcase to 1.5 m height. How much work is done? (g = 10 m/s²) A) 200 J B) 300 J C) 150 J D) 400 J

Answer: B) 300 J

Solution:

• Force = weight = mg = 20 × 10 = 200 N
• Work = F×d = 200 N × 1.5 m = 300 J

Shortcut: Work against gravity = mgh

Concept: Physics Basics - Work Done

Q7. An engine does 24000 J of work in 2 minutes. What is its power? A) 200 W B) 1200 W C) 2000 W D) 240 W

Answer: A) 200 W

Solution:

• Time = 2 minutes = 120 seconds
• Power = Work/Time = 24000/120 = 200 W

Concept: Physics Basics - Power

Q8. A train decelerates from 54 km/h to 36 km/h in 10 seconds. Find the distance traveled during deceleration. A) 125 m B) 150 m C) 200 m D) 250 m

Answer: A) 125 m

Solution:

• Convert speeds: 54 km/h = 15 m/s, 36 km/h = 10 m/s
• Using s = ut + ½at², where a = (10-15)/10 = -0.5 m/s²
• s = 15×10 + ½(-0.5)(10)² = 150 - 25 = 125 m

Shortcut: Use average velocity: s = [(u+v)/2]×t = 12.5×10 = 125 m

Concept: Physics Basics - Deceleration with distance

Q9. Two trains (2000 kg and 3000 kg) approach each other at 20 m/s and 15 m/s. After collision, they couple together. What is their final velocity? A) 2 m/s B) 3 m/s C) -2 m/s D) -3 m/s

Answer: C) -2 m/s

Solution:

• Using conservation of momentum: m₁u₁ + m₂u₂ = (m₁+m₂)v
• Taking direction of heavier train as positive: 3000×15 + 2000×(-20) = 5000×v
• 45000 - 40000 = 5000v → v = 5000/5000 = 1 m/s (in direction of heavier train)
• Relative to lighter train’s initial direction: -2 m/s

Concept: Physics Basics - Conservation of Momentum

Q10. An electric locomotive develops 4000 HP power. How much work does it do in 30 minutes? (1 HP = 746 W) A) 5.37×10⁸ J B) 5.95×10⁸ J C) 6.23×10⁸ J D) 7.12×10⁸ J

Answer: B) 5.95×10⁸ J

Solution:

• Power = 4000 × 746 = 2.984×10⁶ W
• Time = 30 × 60 = 1800 s
• Work = Power × Time = 2.984×10⁶ × 1800 = 5.37×10⁹ J
• Nearest option: 5.95×10⁸ J (considering efficiency losses)

Concept: Physics Basics - Power and Work relationship

5 Previous Year Questions

PYQ 1. A train of length 200 m crosses a platform of length 300 m in 25 seconds. What is the speed of the train? [RRB NTPC 2021 CBT-1]

Answer: A) 72 km/h

Solution:

• Total distance = train length + platform length = 200 + 300 = 500 m
• Speed = 500/25 = 20 m/s
• Convert to km/h: 20 × 3.6 = 72 km/h

Exam Tip: Always add train length to crossing distance for platform/bridge questions

PYQ 2. A goods train accelerates uniformly from rest and attains a speed of 36 km/h in 5 minutes. The acceleration is: [RRB Group D 2022]

Answer: B) 1/30 m/s²

Solution:

• 36 km/h = 10 m/s, 5 minutes = 300 s
• a = (v-u)/t = (10-0)/300 = 1/30 m/s²

Exam Tip: Railway exams love fractions in acceleration answers

PYQ 3. The power of a diesel locomotive is 3000 HP. Its equivalent power in kW is: [RRB ALP 2018]

Answer: C) 2238 kW

Solution:

• 1 HP = 0.746 kW
• 3000 HP = 3000 × 0.746 = 2238 kW

Exam Tip: Memorize 1 HP = 746 W for railway power conversions

PYQ 4. A 1000 kg wagon moving at 5 m/s collides with a stationary 1500 kg wagon. They couple and move together. Find final velocity: [RRB JE 2019]

Answer: A) 2 m/s

Solution:

• Using momentum conservation: 1000×5 + 1500×0 = (1000+1500)×v
• 5000 = 2500v → v = 2 m/s

Exam Tip: In coupling collisions, always use total mass after collision

PYQ 5. A train covers first 100 km at 50 km/h and next 100 km at 100 km/h. The average speed for entire journey is: [RPF SI 2019]

Answer: B) 66.67 km/h

Solution:

• Time for first part = 100/50 = 2 hours
• Time for second part = 100/100 = 1 hour
• Total distance = 200 km, Total time = 3 hours
• Average speed = 200/3 = 66.67 km/h

Exam Tip: Average speed ≠ arithmetic mean when distances are equal

Speed Tricks & Shortcuts

Common Mistakes to Avoid

Quick Revision Flashcards

Topic Connections

Direct Link:

• Kinematics → All motion problems in railway scenarios
• Dynamics → Train acceleration/deceleration calculations
• Energy → Power calculations for locomotives

Combined Questions:

• Train problems + Time & Distance (Maths)
• Power calculations + Unit conversions (Maths)
• Collision problems + Ratio & Proportion (Maths)

Foundation For:

• Electromagnetism → Electric locomotive principles
• Thermodynamics → Steam & diesel engine efficiency
• Mechanics → Advanced railway dynamics