physic
posted by Jeon .
Fernando tosses a ball upwards with an initial velocity of 12.0 m/s. What is in meters/second the velocity of the ball 4.5 seconds after he threw it?

Subtract g*t from the initial (positive) vertical velocity.
t = 4.5 s, and g is the acceleration of gravity, which you should know the value of.
That will give you a negative number, meaning the velocity will be downwards at that time.