Question

A body travelling along a straight line traversed one third of the total distance with a velocity 4 m/s. The
remaining part of the distance was covered with a velocity 2 m/s for half the time and with velocity 6 m/s for
the other half of time. The mean velocity averaged over the whole time of motion is:
(B) 4 m/s
(C) 4.5 m/s
(D) 3.5 m/s
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Answer 1

Answer:

4 m/s is the correct answer

Explanation:

Let 'S' denote the total distance

Let time covered for first one third distance be t1

Then

according to given condition

           t1 = (S/3) / 4 = S / 12

Let t2 be time for next two journeys

      2S / 3 =2 t2 + 6 t2 = 8 t2

   ⇒       t2 = 2S / (12)

We know that

Average velocity = Total distance / Total time

                             =S / (t1 + 2 t2)

By putting

               t1 = S / 12

               t2 = 2 S / 12

we get    

Average velocity = S / { S / (12) + 2 S / (12)  }

                             = 4 m/s

Hence (B) is the correct answer

Answer 2

Answer:This should be the explaination

Explanation: