Two cars moving evenly and in a straight line along two intersecting roads at right angles simultaneously

Two cars moving evenly and in a straight line along two intersecting roads at right angles simultaneously cross the intersection. After a time interval Δt = 20s after passing the intersection, the distance between the cars became (el) l = 500m. Determine the module of speed of the second car, if the speed of movement of the first v (1) = 15m / s

From the condition, the modulus of the speed of the first car and the distance between the cars in time Δt are known. The path traveled by cars is the legs of a right-angled triangle, and the distance l is its hypotenuse. Let’s find the length of the path covered by the first car:
1) l1 = v1 * Δt = 15 * 20 = 300 meters;
By the Pythagorean theorem, knowing the length of the hypotenuse and one and the legs, we find the length of the second leg:
2) l2 ^ 2 = 500 ^ 2-300 ^ 2 = 1600; l2 = 400;
Let’s find the speed with which the second car was moving:
3) v2 = l2 / Δt = 400/20 = 20 m / s
Answer: 20 m / s