Answer: 116.926 km/h
Step-by-step explanation:
To solve this we need to analise the relation between the car and the Raindrops. The cars moves on the horizontal plane with a constant velocity.
Car's Velocity (Vc) = 38 km/h
The rain is falling perpedincular to the horizontal on the Y-axis. We dont know the velocity.
However, the rain's traces on the side windows makes an angle of 72.0° degrees. ∅ = 72°
There is a relation between this angle and the two velocities. If the car was on rest, we will see that the angle is equal to 90° because the rain is falling perpendicular. In the other end, a static object next to a moving car shows a horizontal trace, so we can use a trigonometric relation on this case.
The following equation can be use to relate the angle and the two vectors.
Tangent (∅) = Opposite (o) / adjacent (a)
Where the Opposite will be the Rain's Vector that define its velocity and the adjacent will be the Car's Velocity Vector.
Tan(72°) = Rain's Velocity / Car's Velocity
We can searching for the Rain's Velocity
Tan(72°) * Vc = Rain's Velocity
Rain's Velocity = 116.926 km/h