We are given a watermelon dropped at free fall from a building 320 meters above the sidewalk. Superman is headed down at 30 meters per second. We are asked to determine how fast is the watermelon going when it passes Superman. To solve for the final velocity of the watermelon, we will use one of the kinematic equations (free fall):
vf = vi + a*t
where vf is the final velocity
vi is the initial velocity, zero
a is the acceleration, in this case, gravitational acceleration = 9.8m/s^2
t is time
we also need to set-up another equation using the distance:
d = vf + vi / 2 * t
(1) 320 m = vf * t /2
(2) vf = 9.8 m/s^2 * t
From here, we have two equations and two unknown, thus we can solve the problem by substitution.
