If a component of acceleration a_x is equal to zero
during some interval, then the component of velocity in that direction,
v_x, remains constant during that interval. In this case you can apply
the following equations to the the x components of motion:
-
vf_x = vi_x
final velocity component = initial velocity component
-
d_x = vi_x * t
x component of displacement = constant velocity component * time
where vi_x and vf_x are the x-components of the initial and
final velocities of the object and d_x is the x-component of the displacement
of the object.
These relations are special cases of the constant
acceleration equations for the case when acceleration is zero.
Tip: To avoid making sign errors, always write these equations in terms
of the vector components, then rewrite it in terms of magnitudes if necessary
by substituting in projection equations.
Note that these equations may apply only to one component of the motion.