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Two cars, P and Q start from the same place but Q starts 1 hour late. Ther travel along the same road. P and Q have 80kmph and 100kmph respectively. Find the time taken for Q to overtake P

Two cars, P and Q start from the same place but Q starts 1 hour late. Ther travel along the same road. P and Q have 80kmph and 100kmph respectively. Find the time taken for Q to overtake P

Grade:11

4 Answers

Khimraj
3007 Points
7 years ago
You can easily solve by concept of relative velocity. Relative displacement is 80 km and velocity 20km/HR. So time taken to cover this time is 4 HR and time to overtake is 5 hr as Q start one hour late.Hope it clears. If u have doubts then please clearify. And if u like my answer then please approve answer.
Vidura
20 Points
7 years ago
What is your final answer? 
I made it like this …........
s=ut(P)
  =80xt
  =80t
 
s=ut(Q)
  =100x(t-1)
  =100t-100
 
As Q overtakes P they should have travelled the same distance at that instance …....
Distance travelled by P equals to that of Q,
 
80t=100t-100
20t=100
t=5hrs
Khimraj
3007 Points
7 years ago
Yes and is 5 hr.Hope it clears. If u have doubts then please clearify. And if u like my answer then please approve answer.
Vidura
20 Points
7 years ago
I too hoped the answer would be 5 but unfortunately the answer is 4. It should be either our mistake in making the sum or the answer in that particular text book is wrong.

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