A train 120 meter long passes an electric pole in 12 seconds and another train of same length traveling in opposite direction in 8 seconds. The speed of the second train is

• speed of 1st train=120/12=10m/s
  let the speed of 2nd is v
  then
  240/(v+10)=8
  8v=160
  v=20m/s ANS.
• 13 years agoHelpfull: Yes(30) No(13)
• speed pf the second train=12/8=15m/sec
• 13 years agoHelpfull: Yes(11) No(20)
• speed of 1st train is 120/12=10m/s
  now their lengths are same, so s1*t1=s2*t2 or, s2=s1*t1/t2=10*12/8= 15m/s
  here there is no need to think about opposite direction, as relative speed is not asked...
• 13 years agoHelpfull: Yes(8) No(11)
• Pole is given for us to just calculate the speed of 1st train .
  Speed = 120/12 = 10m/s
  Now Concept of relative speed
  Let speed of 2nd train be v.
  Since both trains are traveling in opp. direction
  relative speed = 10+v
  Total distance will be sum of length of both the trains.
  Total dist = 120+120 =240
  Time is 8 sec
  Dist/speed=time
  240/(v+10)=8
  v=20m/s
  i.e. 72km/hr.
• 9 years agoHelpfull: Yes(8) No(2)
• speed=distance/time
  for second train:
  speed=120m/8s=15m/sec
• 13 years agoHelpfull: Yes(7) No(7)
• Train covers 120 meters in 12 seconds, therefore
  speed of first train =120/12=10 m/s
  let speed of second train be x m/s. Trains are approaching each other, therefore there relative speed is (10+x)m/s.
  Trains have to cover a distance equal to the sum of length of both trains which is 120+120=240 m.
  time taken to cross the trains i.e. 240 m is 8 sec
  Thus 240/(10+x)=8 , by solving we get
  x = 20 m/s = 20*3600/1000 km/hr = 72 kmph
• 8 years agoHelpfull: Yes(1) No(0)
• from the first part of question we can comfortably say that
  the speed of first train is 10m/s(120m/12sec)..
  from the second part
  since the two trains are moving in opposite directions
  speed of train a=10m/s
  speed of train b=x m/s(just consider the magnitude)
  since train a crosses b in 8 secs.that means end point of a
  crosses the end point of b after 8 secs.
  we ASSUME B TO BE AT REST
  and a moves toward b with speed =(10+x)m/sec
  therefore distance to be covered =240m
  time=8secs
  (10+x)=240/8;
  x= 20m/sec
• 8 years agoHelpfull: Yes(1) No(0)
• question has got nothing to do with the time of first train....except the length of it.speed of second train is 120/8=15m/s
• 7 years agoHelpfull: Yes(0) No(0)