Question

50 m long trains are crossing each other in opposite direction with velocity of 10 m/s and
15 m/s. respectively Then time-taken by trains to cross each other will be-
(1) 2 sec.
(2) 4 sec.
(3) 6 sec.
(4) 8 sec​

Answer 1

AnswEr :

⠀

$\scriptsize\blacksquare~\underline{\mathfrak{Diagram~for~Refrence}}$

⠀

▣ Distance of 1st Train = 50 m

▣ Velocity of 1st Train = 10 m/s

▣ Distance of 2nd Train = 50 m

▣ Velocity of 2nd Train = 15 m/s

━━━━━━━━━━━━━━━━━━━━━━━━

◨ Total Distance to be Covered

» 50 m + 50 m

[ One Train Cover in Respect to Other ]

» 100 m

◨ Relative Speed of one Train with Respect to Other

» 10 m/sec - (- 15) m/sec

[ As they're Moving in Opposite Direction ]

» ( 10 + 15 ) m/sec

» 25 m/sec

━━━━━━━━━━━━━━━━━━━━━━━━

☢ We Know the Formula ;

$\large \boxed{ \bold{Distance = Speed \times Time}}$

Plugging in the Values :

$\longrightarrow \large \bold{100m = 25m/sec \times Time \: }$

$\longrightarrow \large \bold{ \frac{100m}{25m/sec} = Time \: }$

$\longrightarrow \huge \bold{Time = 4 \: sec}$

$\large\therefore$ Time taken by trains to Cross Each Other will be [ 2 ] 4 sec.

Answer 2

$\large \mathfrak{Answer : }$

• Length of each train = 50 m

★ Effective distance to be covered by each train to cross over :

=> 50 + 50

=> 100 m

• Velocity of first train = 10 m/s

• Velocity of second train = 15 m/s

★ Relative velocity

=> 15 - (-10)

=> 25 m/s

___________________________________

➡ Time Taken = Distance / Speed

➡ Time Taken = $\large\tt{\frac{100}{25}}$

➡ Time Taken = 4 sec

So, Correct Option is (2) 4 sec.