Model 3 Train Vs Bridge/Platform Section-Wise Topic Notes With Detailed Explanation And Example Questions

Answer: (c)

Let the length of train be x metre.

When a train crosses a platform, distance covered by it

= length of train and platform.

Speed of train

= ${x + 50}/14 = x/10$

${x + 50}/7 = x/5$

7x = 5x + 250

7x - 5x = 250

2x = 250 ⇒ x = $250/2$ = 125 metre

Speed of train = $x/10$

= $(125/10)$ m./sec.

= $(125/10 × 18/5)$ kmph = 45 kmph.

Answer: (b)

Speed of train

= $\text"Length of (train + platform)"/ \text"Time taken in crossing"$

= ${(50 + 100)}/10 = 150/10$ = 15 m/sec

Answer: (c)

Speed of train

= $\text"Lengthof(train + platform)"/ \text"Timetaken tocross"$

= $({500 + 700}/10)$ feet/second

= 120 feet/second

Using Rule 10,

Here, x = 500 feet, y = 700 feet

t = 10 seconds, u = ?

using t = ${x + y}/u$

u = ${500 + 700}/10$

= 120ft/second