Question

The average speed of an object over a given time duration is 6m/s. If it travels first half of the duration with a constant speed 4m/s ,it's speed during the next half duration is what?

Answer 1

Step 1 . Calculating net distance

Suppose the object takes time t to complete the journey.

It travels for time t/2 at speed 4 m/s. So, the distance traveled in this t/2 is

=time multiply by velocity = $4\times \frac{t}{2}=2t$

Let It travels the next time t/2 at speed v m/s.

So, the distance travelled in this t/2 is =time multiply by velocity= $v\times \frac{t}{2}=\frac{vt}{2}$

Step 2 .Calculating average speed

Now, Average speed = total distance/total time

$\frac{2t+\frac{vt}{2}}{t}=6$

$itgivesv=\frac{8m}{sec}$

Final answer - speed in second half is 8m/sec