Agirl throws a tennis ball upward with an initial velocity of 4 m/s. what is the maximum displacement of the ball?
a.) 0.2m up
b.) 0.4m up
c.)0.8m up
d.)1.6m up

This is done using the following equations of straight-line motion:

Vf = Vi + a*t

Where: Vf = final velocity
Vi = initial velocity
a = acceleration (in this case, gravity)
t = time

We first have to determine how long it stays in the air on the way up. Substituting the given values and solving for t:

0 = 4 + (-9.8)*t
t = -4 / -9.8
t = 0.41s

Using the following equation to solve for displacement, s:

s = Vi * t + 1/2 (a*t^2)
s = 4*0.41 + 1/2 ((-9.8)(0.41^2))
s = 0.81 m

Therefore, the displacement of the ball upwards is 0.8 meters. Among the choices, the correct answer is C.