# Homework Help: Velocity question help?

1. Sep 3, 2007

### arpitm08

velocity question help???

1. The problem statement, all variables and given/known data
A car is going at 50 km/h due east. Water is falling vertically with respect to the earth. Looking at the side windows the water creates a 60 degree angle with the vertical. What is the velocity of the water with respect to
a) car
b) earth.

2. Relevant equations

I don't know how to solve, so I don't know any relevant equations.

3. The attempt at a solution

Did not know how to approach. Could someone please clear this up for me. These type of "with respect to" questions are really confusing for me.

2. Sep 3, 2007

### Astronuc

Staff Emeritus
Draw a 30-60-90 (right) triangle, with the 60 in the upper vertex (angle between hypotenuse and vertical leg).

The car travels a distance 50 km/h*T, and make that the length of the base.

In the same time T, the rain falls distance Vrain*T. Make that the other leg.

What is relationship between Vcar = 50 km/h and Vrain?

3. Sep 3, 2007

### arpitm08

Tan 60 = 50 km/h / Vrain
Vrain=28.87 km/h

So that is the velocity of the rain with respect to the car. Would you just solve for the hypotenuse to get the velocity of the rain with respect to the earth.

4. Sep 4, 2007

### rootX

just use trignometry...

5. Sep 4, 2007

### Astronuc

Staff Emeritus
The 28.9 km/h is the velocity (speed actually) of the rain (falling).

The hypotenuse would give the apparent velocity of the rain as observed from the car.