IIT JEE , AIEEE Forum - Physics , Mechanics

tarun_bits

The driver of the train moving at 20 m/s sights another train moving at 4 m/s on the same track and in the same direction.He immediately applies brakes and his train beging to retard at 1 m/s. What should be the minimum distance between the trains for no collison?

priyesh

see

velocity of train w.r.t the other train is 20 -4 = 16m/sec

now using v^2 - u^2 = 2as

where u = 16 , a = -1 , v =0

we get s = 128m

therefore minimum distance should be 128m

tarun_bits

ya thanx

raman_shadow

yaar let d train at A be at 20 m/s. and at B be 4 m/s.
Let d coll. is just avoided at C where vel. of both trains is 4 m/s.

for train at A until C using v² - u² = 2as
16 - 400 = -2(d + x)
d + x = 192 ......................................(1)

using v = u + at for same part
4 = 20 - t
t = 16

for train at B using speed = dist/time
dist, d = 4*16 = 64

put d in (1)

x = 128
so min dist. b/w 2 trains shud be 128 m

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