Near the surface of the earth if air resistance is negligible, the x and y components of position, velocity, and acceleration of a projectile are independent.  Therefore, you can consider a projectile thrown at some angle as having the motion of two similar projectiles, one that travels upward with a constant downward acceleration and one that travels horizontally at constant velocity.

Answer the following questions:

1.  What direction is the velocity vector when the projectile is at its peak?

2.  Is the time in the air determined by the initial x-velocity or the initial y-velocity or both?

3.  Is the maximum height obtained determined by the initial x-velocity or the initial y-velocity or both?

4.  Is the maximum horizontal displacement determined by the initial x-velocity or the initial y-velocity or both?

 
X Position vs Time
 Y Position vs Time

Ball thrown at an angle from the ground