What are the equations for projectile motion on an inclined plane?

[Big-Daddy]

Homework Statement

A particle of mass m is projected with velocity of magnitude u at an angle of θ, measured anticlockwise from the line parallel to the plane, from a point (s_x,0,s_y,0) on a plane inclined at an angle of α measured anticlockwise from the line parallel to the ground. The particle coordinates refer to the particle's initial position (it starts from the plane) relative to the ground (i.e. s_x is on an x-axis parallel to the ground, s_y is on a y-axis perpendicular to the ground).
Find an expression each for s_x and s_y in times of time t, given that the particle undergoes no horizontal acceleration and that its only vertical acceleration is -g ms^-2.

Homework Equations

I don't know. We have to find the equation.

The Attempt at a Solution

Well if the plane were not inclined this would be pretty easy.

$${s_y} = u \cdot \sin{θ} \cdot t + \frac{1}{2} \cdot {a_y} \cdot t^2$$

$${s_x} = u \cdot \cos{θ} \cdot t$$

Where θ is the angle of projection, and a_y happens to be -g=-9.8 ms^-2 in this case.

But now that the plane is inclined, I really am not sure!

 

[rude man]

Gives me a headache just to figure the problem.

Would be good if the initial velocity were given in terms of v = vx i + vy j + vz k as well as its initial position (x0, y0, z0). Or if it's 2-dimensional (I can't tell from the wording), leave out the z0 and vz k. Then we could compute x(t), y(t) and (if appropriate) z(t).