There can always be up to three components of velocity.
Usually in projectile motion, there will be two, because we align one of the horizontal axes with the direction of horizontal motion. There is no reason for a projectile to change its horizontal direction.
Even if the initial velocity is purely horizontal, it will not remain purely horizontal. Eventually as if falls, its vertical velocity component will increase in magnitude.
"Gravity doesn't take a holiday on objects just because they are moving"
http://www.youtube.com/watch?v=qErh402eJ…
Usually in projectile motion, there will be two, because we align one of the horizontal axes with the direction of horizontal motion. There is no reason for a projectile to change its horizontal direction.
Even if the initial velocity is purely horizontal, it will not remain purely horizontal. Eventually as if falls, its vertical velocity component will increase in magnitude.
"Gravity doesn't take a holiday on objects just because they are moving"
http://www.youtube.com/watch?v=qErh402eJ…
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2.... the horizontal velocity, and the vertical acceleration due to gravity can give a final vertical velocity.