Two cars are 500 cm apart. each is moving forward for 100 cm at a velocity of 50 cm/s and receding back for 50 cm at 25cm/s at what time they will collide with each other.

• each car is moving forward for 100 cm with velocity 50cm/s
  so time to cover 100cm is=100/50=2 sec
  again receding back for 50 cm at 25cm/s velocity
  so time to cover 50 cm is=50/25=2 sec
  actually they individually cover (100-50)=50 cm in (2+2)=4 sec
  so in 12 sec they together cover (150+150)=300 cm
  and after that both move 100 cm in 2 sec
  so after (12+2)=14 sec they cover (300+200)=500cm
  so they collide after 14 sec
• 13 years agoHelpfull: Yes(29) No(3)
• total distance = 500cm
  each car has to travel 250 cm to collide with each other
  
  now, a car travels 100 cm forward with 50 cm/s speed => time taken = 2 secs
  and 50 cm backward with a speed of 25 cm/s => tiime taken = 2 sec
  so, for 4 secs each car travels 100 - 50 = 50 cms..
  each car has to travel 250 cms to collide
  
  from this point car will touch 150 cm in 6 sec (as after we got from above that car already travelled 50 cms) and then come back 50 cms in next two second
  
  so actual distance travelled = 100 cms
  actual time taken = 8 secs
  
  in this way car again touch the 200 cm mile stone in next 2 secs and come back 50cm in next 4 secs
  actual distance travelled in 12 secs is 150 cms
  
  now actual distance is to travell 250 cms so remained is only 100 cms which the car will travell in next 2 secs and then collide
  
  so the car will collide in 14 secs
  
  so both cars collide after 20 secs.
• 13 years agoHelpfull: Yes(10) No(8)
• each is moving forward for 100cm at velocity 50cm/s and receding back for 50 cm at 25cm/s i.e in 4s every car covered 50cm
  so every car has t covered 250cm path
  
  So it takes (250/50)*4=20s when they meet
• 13 years agoHelpfull: Yes(2) No(8)
• answer shuold be 14sec .previously submiited wrong answer
  
• 8 years agoHelpfull: Yes(2) No(0)
• This is the "Frog in the Well" problem.
  
  The question is: "How long does it take a car to move 250 cm forward?"
  
  
  We can baby-step through the solution.
  
  Draw a number line for reference.
  
  . . begin{array}{cccccccccccc}
  bullet & -- & bullet & -- & bullet & -- & bullet & -- & bullet & -- & bullet \
  0 && 50 && 100 && 150 && 200 && 250 end{array}
  
  
  In 2 seconds, it moves 100 cm forward.
  In the next 2 seconds, it moves 50 cm back.
  It is at "50".
  . . In 4 seconds, it moved 50 cm forward.
  
  In the next 4 seconds, it moves 50 cm forward.
  . . It is at "100".
  
  In the next 4 seconds, it moves 50 cm forward.
  . . It is at "150".
  
  In the next 2 seconds, it move 100 cm forward.
  . . It is at "250".
  
  
• 8 years agoHelpfull: Yes(1) No(0)
• if both cars are moving forward separated by a distance moving at same rate, will they collide?
• 8 years agoHelpfull: Yes(1) No(1)
• answer shold be 7sec
• 8 years agoHelpfull: Yes(0) No(2)
• the ans is 20 secs
  as each car covers 50 cm in 4 secs so in first 4 secs both moves towards each other i.e 50+50=100 cm in 4 sec.
  so,500 cm in 4*5=20 secs
• 8 years agoHelpfull: Yes(0) No(0)