Question

Raindrops make an angle with the vertical when viewed through a moving train
window. If the speedometer on the train is showing that the speed of the
train is v , what is the speed of the raindrops in the reference frame of the Earth
in which they are assumed to fall vertically?

Answer 1

terminal velocity for a rain drop. assuming theses rain drops started to fall to the ground high enough to reach that speed. the stuff about the train and viewing the rain drops is i irrelevant. the question asked about the velocity of the drops compared to the ground

Answer 2

Their speed is (speed of the train) times (cotangent of the angle the drops appear to make with the vertical).