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Two trains, each of length 200 m are run...

Two trains, each of length 200 m are running on parallel tracks. One overtakes the other in 20 s and one crosses the other in 10 s. The velocities of the two trains are :

A

5 m/s, 10 m/s

B

10 m/s, 30 m/s

C

15 m/s, 5 m/s

D

20 m/s, 21 m/s

Text Solution

Verified by Experts

The correct Answer is:
B
Let velocities of two trains be u and v.
Relative velocity while overtaking = u - v
Relative velocity while crossing = u + v
Distance travelled in each case `=200+200=400m`
`therefore" "20=400/(u-v)`
`therefore" "u-v=(400)/20=20" ...(1)"`
`" "u+v=400/10=40" ...(2)"`
From Eqs. (1) and (2), we get
u = 30 m/s, v = 10 m/s
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