A car moves 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. `56km h^(-1)`
B. `60km h^(-1)`
C. `50 km h^(-1)`
D. `48km h^(-1)`

Answer

b

Explanation

For the first half let time taken be `t_(1)`
`t_(1)=(100m)/(40kmh^(-1))`
For the second half let time taken be `t_(2)`
`t_(2)=(100)/(v)`
Average velocity `=("total displacement")/("total time")`
`48=((200xx10^(-3))km)/((10^(-3)xx100)/(40km//h)+(100xx10^(-3))/(v))`
`48=(2(40v))/(v+40)`
`48v+40xx48=80v`
`v=60km h^(-1)`