The bird flies at a speed of 18 km / h, and a wind blows at a speed of 7.2 km / h perpendicular to its movement.

The bird flies at a speed of 18 km / h, and a wind blows at a speed of 7.2 km / h perpendicular to its movement. Find the module of the bird’s movement speed relative to the ground.

Vpt = 18 km / h = 5 m / s.
Vvet = 7.2 km / h = 2 m / s
V -?
The speed of the bird relative to the ground V will be the vector sum of the bird’s own speed Vпт and the wind speed Vvet.
The bird’s ground speed module will be the hypotenuse in a right triangle.
Let us find the length of the hypotenuse by the Pythagorean theorem: V ^ 2 = Vпт ^ 2 + Vvet ^ 2.
V = √ (Vпт ^ 2 + Vvet ^ 2).
V = √ ((5 m / s) ^ 2 + (2 m / s) ^ 2) = 5.39 m / s.
Answer: the speed of the bird relative to the ground is V = 5.39 m / s.