How Does a Particle's Position Change with Acceleration in the XY Plane?

[im4rheal]

Homework Statement

A particle leaves the origin with a velocity of 7.2 m/s in the positive y direction and moves in the xy plane with a constant acceleration of (3.0i - 2.0j) m/s². At the instant the particle moves back across the x-axis (y=0), what is the value of its x coordinate?

Homework Equations

v_xf=v_xi+a_xt
x_f=x_i+.5(v_xf+v_xi)t
x_f=x_i+v_xit+.5a_xt²
v²_xf=v²_xi+2a_x(x_f-x_i)

The Attempt at a Solution

Are my x and y initial (0,0) because it says origin? Do I have to used to substitution as well?

 

[JayneDoe]

Starting at the origin does mean that x_i=y_i=0, yes.

I'm not entirely sure what your second question means, but you should be able to formulate an expression for both the x and y position of the particle at any given time and then use substitution to find the answer.