Question

1. Two cars are moving in the same direction with the same speed 30 km /hr. They are separated by a distance of 4 km. What is the speed of a car moving in the opposite direction if it meets these two cars at an interval of 5 minutes?

Answer 1

Let the two cars moving in the same direction with the same speed 30 km/h be 'A' and 'B'.

Seperation between car A and B = 4 km

Let the third car moving in opposite direction be 'C' which meets car A and B at an interval of 5 min.

Let the speed of car C be 'x'

Relative speed of car A and car C = 30 + x

Relative distance = 4 km

Time taken = 5 min

= $\sf \dfrac{5}{60}$ h

= $\sf \dfrac{1}{12}$ h

So,

$\bf \implies Speed = \dfrac{Distance \: travelled}{Time \: taken} \\ \\ \rm \implies 30 + x = \dfrac{4}{ \dfrac{1}{12} } \\ \\ \rm \implies 30 + x = 4 \times 12 \\ \\ \rm \implies 30 + x = 48 \\ \\ \rm \implies x = 48 - 30 \\ \\ \rm \implies x = 18 \: km {h}^{ - 1}$

$\therefore$ Speed of third car moving in opposite direction = 18 km/h

Answer 2

Answer:

450 km/h

Explanation:

scince the two cars are moving in the same direction with same speed therefore relative speed between two cars is zero.

Let the relative speed of the third car be w.r.t the two cars

Relative velocity of the third car : (5/30×30=60)h ×40km

Actual velocity of the third car = 480-30 = 450km/h .