# Homework Help: Projectile motion vector problem

1. Nov 7, 2009

### velocityay

1. The problem statement, all variables and given/known data
At what compensatory angle north of east should a drone, that can only move forward at a maximum speed of 20 m/s, be launched if it is to strike a target that is 400m due east if there is a wind moving 5 m/s south?

2. Relevant equations
vx=20cos$$\Theta$$
vy=20sin$$\Theta$$

3. The attempt at a solution
I'm not sure how to start trying to solve this, I drew a small diagram labeled with north south east and west and it shows the object's trajectory over the 400 m. I set up a chart of known and unknown variables
x
d=400 m
a=0 m/s2
t= ?
vi=20cos$$\Theta$$
vf=20cos$$\Theta$$
vavg=20cos$$\Theta$$

y
d=?
a=9.8 m/s2
t=?
vi=20sin$$\Theta$$
vf=?
vavg=?

that's all I can get

2. Nov 7, 2009

### Jack21222

First define your variables. What is x and what is y? Why is acceleration in the y direction 9.8 m/s^2?

3. Nov 7, 2009

### velocityay

x is motion on the axis from west to east and y is motion on the axis from south to north, the acceleration in the y direction is that because the only force acting on it is the gravitational force

4. Nov 7, 2009

### Jack21222

Gravity doesn't work from north to south.

EDIT: My point is, you're approaching the problem from completely the wrong angle. It's simple vector arithmetic and trigonometry. Try re-drawing the problem with that in mind, and let us know how you do.

Last edited: Nov 7, 2009