From one point at the same time in opposite directions two cars are sent at a constant speed.

From one point at the same time in opposite directions two cars are sent at a constant speed. modules of vehicle speeds v = 54 km / h and v = 90 km / h, respectively. After what time interval the distance between them will be l = 12 km

V1 = 54 km / h = 15 m / s.

V2 = 90 km / h = 25 m / s.

l = 12 km = 12000 m.

t -?

Since the cars left the same point in opposite directions, the distance between them l will be the sum of the distances that each car traveled: l = l1 + l2.

With uniform rectilinear movement, the path l passed by the body is the product of the speed of movement V and the time of movement t: l = V * t.

l1 = V1 * t.

l2 = V2 * t.

l = V1 * t + V2 * t = (V1 + V2) * t.

t = l / (V1 + V2).

t = 12000 m / (15 m / s + 25 m / s) = 300 s = 5 min.

Answer: the specified distance between them will become in time t = 5 minutes.