Projectile motion is the superposition of two independent motions:

Horizontal (x-direction):

• $a_x$ = 0 (no air resistance)
• $v_x$ = u*cos(theta) = constant throughout flight
• x = u*cos(theta) * t

Vertical (y-direction):

• $a_y$ = -g (upward positive)
• $v_y$ = usin(theta) - gt
• y = u*sin(theta)t - $\frac{1}{2}$g$t^2$

Independence principle: Horizontal and vertical motions do not affect each other. A bullet fired horizontally and one dropped from the same height hit the ground at the SAME time.

Equation of trajectory (eliminate t): y = xtan(theta) - g$x^2$ / (2*$u^2$*$cos^2$(theta))

This is a parabola (y = ax - $bx^2$ form).