Train Crossing Concept Explained in 59 Seconds! | JEE Speed-Time Physics

🚆 Train Crossing Concept in 59 Seconds | Doubtify JEE Shorts

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📌 Question:

Ever wondered how long one train takes to pass another or a platform? The Train Crossing Concept helps solve such questions in seconds using speed-distance fundamentals.

📕 Concept & Formula:

1. Same Direction:

$$\text{Time} = \frac{\text{Length of Train A + Length of Train B}}{\text{Relative Speed}} \quad (v_{rel} = v_1 - v_2)$$

2. Opposite Direction:

$$\text{Time} = \frac{\text{Length of Train A + Length of Train B}}{\text{Relative Speed}} \quad (v_{rel} = v_1 + v_2)$$

3. Train Passing Platform or Pole:

$$\text{Time} = \frac{\text{Length of Train}}{\text{Speed of Train}}$$

Speeds should always be converted to m/s when lengths are in meters

$$1 \text{ km/hr} = \frac{5}{18} \text{ m/s}$$

🔢 Example:

A train of 120 m length moving at 60 km/hr crosses a platform of 180 m length.

$$\text{Total Length} = 120 + 180 = 300 \text{ m} \text{Speed} = 60 \times \frac{5}{18} = 16.67 \text{ m/s} \Rightarrow \text{Time} = \frac{300}{16.67} \approx 18 \text{ sec}$$

🧠 JEE Tip:

• Always convert km/hr to m/s

• Be careful about same vs opposite direction in relative speed

• Draw diagrams for clarity

• These questions are common in JEE Mains Kinematics

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🖼️ Image:

🎥 Watch 59-Second Concept Video:

🧠 Pro Tip:

Don’t cram formulas – visualize the motion! Once you do that, solving becomes intuitive.

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