# Projectile Question

1. Sep 16, 2008

### dsptl

A car is moving with constant velocity along a slope as shown in the figure. The magnitude of the velocity is 10m/s. Find the position of point A where the car hits the ground.

Angle = 20 degree
Height = 20m

2. Sep 16, 2008

### danago

What is the initial velocity in the vertical and horizontal directions?

3. Sep 16, 2008

### dsptl

i think

Vy = 10sin20degree

Vx = 10cos20degree

4. Sep 16, 2008

### danago

Alright, now how can you determine how long before it hits the ground?

5. Sep 16, 2008

### dsptl

y = vi * t + .5at*t

20 = 3.4t - 5t*t

6. Sep 16, 2008

### danago

You need to be careful of your signs. You have acceleration as negative there, but you have both displacement and velocity as positive, even though they are in the same direction as acceleration here. If you try to solve that you will get complex solutions.

7. Sep 16, 2008

### dsptl

so is it like

-20 = -3.4t - 5t*t

8. Sep 16, 2008

### Dschumanji

Is the positive y direction in your coordinate system pointing downward?

9. Sep 16, 2008

### danago

Thats better.

10. Sep 16, 2008

### dsptl

then I just multiply t by Vx to get the ans

thx a lot 4 the help