Two balls are launched simultaneously from the same height. Ball A is released from rest, and drops straight down. Ball B is given an initial horizontal velocity.

Which ball hits the ground first?

- Ball A
- Ball B
- Both balls hit the ground at the same time

Key point: * Independence* of x and y!. The
vertical and horizontal motions are independent. This means that both balls
hit the ground at the same time.

Basic consequence: Two-dimensional projectile
motion can be viewed as two *
independent* one-dimensional motions.