# Kinematics of moving car and falling rain

1. Aug 31, 2008

### devanlevin

a man driving his car on a straight road at 25m/s looks through his side windows and sees rain fallling at 30 degrees. when he stops he sees the rain is actually falling straight down(0 degrees).
what is the velocity of the rain, relative to the car
a- when the car is moving
b- when the car is stopped

i said, since the car is driving, it is giving the rain Vx=25m/s (relative to the car) and since i know the angle is 30 degrees

a)
sin30=(Vx)/V
V=25/sin30
V=50m/s

b)
cos30=Vy/v
Vy=50*cos30
vy=43.301

but the answer in my text book says that the rains velocity is 25m/s for question b) and 28.86 for a)

2. Aug 31, 2008

### Solaxys

Re: kinematics

switch the sin and cos in both questions :p.

So use cos in the a)
and sin in b)

3. Aug 31, 2008

### devanlevin

Re: kinematics

haha, works,
but wouldnt that mean that he sees the rain falling at 60 degrees??

4. Aug 31, 2008

### Solaxys

Re: kinematics

I think the question means 30 degrees, relative to the ground or the horizontal, rather than the vertical.