Question

. A body moves with the speed of 40Km/h for half an hour and with the speed of 60km/h in the next half an hour. The average speed of the body is



48km/h

49km/h

60km/h

50km/h

​

Answer 1

Answer:

A body moves with the speed of 40Km/h for half an hour and with the speed of 60km/h in the next half an hour. The average speed of the body is

$48\ km/h$.

Explanation:

If $v_1$ is the velocity in the first half an hour and $v_2$ is the velocity in the second half an hour.        

Then,

We have the expression for average speed as,  

Average speed = $\frac{2 v_1 v_2}{v_1 +v_2}$     ...(1)

In the question, it is given that,

$v_1 = 40\ km/h$           $v_2 = 60\ km/h$    

Substitute these values into equation (1)

we get,

Average speed =  $\frac{(2\times 40\times 60)}{40 +60} = \frac{4800}{100} = 48\ km/h$

So the first option is the correct answer.