Problem Solving with g= 9.8 m/s2

Question

A ball is thrown straight up with a velocity of 16 m/s; what will be its velocity 2.0s after

being released?

Answer 1

You know that the ball starts with a velocity upward of 16 m/s. g = 9.8 m/s^2 means that every second, the velocity changes by 9.8 m/s in the downward direction. In other words, acceleration (a) = -9.8 m/s^2. So after 2 seconds, the velocity will be Vf = Vi + a*t:

(16 m/s) + (-9.8 m/s^2)(2 s) = -3.6 m/s

We defined upward as positive and negative as downward, so the ball will be moving at 3.6 m/s downward.