A cae movies a distance of ` 200 m`. It covers the first half of the distance at speed of ` 40 km//h` and second half of the distance at a speed (v). The average speed is ` 48 km//h`. Find the value of (v) .

Options

A. (a) ` 56 km//h`
B. (b) ` 60 km//h`
C. (c ) ` 50 km //h`
D. (58 km//h`

Answer

B

Explanation

Here ` S = 200 m = 0.2 km, ` v_1 = 40 km//h, `v_2 = v`
Average velocity = (total displacement )/(total time )`
or ` 48= ( 0.2)/t`
`t= 90.2)/(48),
For first half distance ` S-1 = 100 m= 0.1 km`
:. T-1 =(0.1)/(40) similarly` t_2 = (0.1)/v`
` t=t_1 +t_2 `or (0.2)/(48) = (0.1) (40) + (0.1)/v`
(0.2)/(48) - ( 0.1)/(40) = (0.1)/v` on soving we get, ` v = 60 km/h`.