A locomotive driver travelling at 72 km/hr finds a signal 210 metres ahead of him indicating he should stop. He instantly applies brakes to stop the train. The train retards uniformly and stops 10 metres before the signal post. What time did he take to stop the train?

• 72kmph=20m/s....train travels 200mts before stoppin...so time taken=200/20=10 sec
• 11 years agoHelpfull: Yes(12) No(2)
• v^2-u^2 = 2as
  here v=0
  u= 72 kmph = 72*5/18 = 20m/sec
  s= 200m
  hence a= -(20^2)/2*200 = -1 m/sec^2
  a=(v-u)/t
  t= (v-u)/a= -20/-1= 20 secs
• 11 years agoHelpfull: Yes(8) No(3)
• we know that speed=dist/time
  therefore speed=72km/hr=72*5/18=20m/sec
  now train is stopping before 10m from signal than req dist is 210-10=200m
  hence time=distance/speed
  time=200/20=10sec
  therefore time required to stop the train is 10seconds
  
• 11 years agoHelpfull: Yes(4) No(1)
• @ Aziz and raghvendra,
  
  Pls check this statement.
  The train retards uniformly and stops 10 metres before the signal post.
  Speed is reducing. It is not constant at 20m./sec.
• 11 years agoHelpfull: Yes(4) No(1)