Question

j) On a 60 km straight road, car travels first 30 km with uniform speed of 30 km /hr. How fast
it should travel next 30 km to have speed 40 km/hr for entire trip?



pls give answer fast​

Answer 1

distance = speed / time

30 km = 30 km /hr

30 km

Answer 2

Given :

▪ A car travels first 30km at a speed of 30kmph.

▪ Total length of path = 60km

To Find :

▪ How fast it should travel next 30km to acquire average speed of 40kmph.

Concept :

↗ Average speed is defined as the ratio of total distance travelled to the total time taken.

↗ It is a scalar quantity.

↗ It can't be negative or zero.

↗ SI unit : m/s

Calculation :

➡ If body covers first half of total distance at a speed of V1 and second half of total distance at a speed of V2, then average speed of body is given by

$\implies\bf\:V_{av}=\dfrac{2V_1V_2}{V_1+V_2}\\ \\ \implies\sf\:40=\dfrac{2\times 30\times V_2}{30+V_2}\\ \\ \implies\sf\:1200+40V_2=60V_2\\ \\ \implies\sf\:20V_2=1200\\ \\ \implies\underline{\underline{\bf{V_2=60kmph}}}$