You're driving on the freeway going 90km per hour and it starts to rain. The raindrops make an angle of 40 degrees with the vertical when viewed through the driver's side window.

Question

What is the speed of the raindrops measured by someone at rest relative to the freeway? What is the speed of the raindrops relative by you?

Answer 1

drop speed relative to rest
... s = 90 kph / tan(40º)

drop speed relative to vehicle
... s = 90 kph / sin(40º)