How Can the Windscreen Angle Prevent Rain from Entering the Cart?

[f(x)]

Homework Statement

A glass wind screen whose inclination with the vertical can be changed, is mounted on a cart as shown in figure. The cart moves uniformly along the horizontal part with a speed = 6 m/s. At what max. angle \ \theta to the vertical can the wind screen be placed so that the rain drops falling vertically downwards with velocity = 2m/s DO NOT enter the cart ?
___________
|**********|\
|***CAR****|..\ <--WINDSCREEN
|**********|...\
|**********|
|___________|

2. What I need help with
This problem i am unable to start off
I am not able to judge the (relative) velocity vectors. I cannot decide the condition for the rain drops to not enter the car.
Thx for any help

 

[chaoseverlasting]

Assume that the car is at rest and the rain is falling at some angle to it. So, the vertical comp of the rain is given and the horizontal component will be that of the car (but with the direction reversed).

Now, assume that the rain falls in a straight line and that should give you something to work with.