Answer:
C
Explanation:
The acceleration will be negative, as in the problem statement, the upwards direction is defined as positive (the object is shot upwards and has a positive velocity), so immediately, we can eliminate A and B.
You can then use the kinematics equation:
[tex]v=v_o+at[/tex], where
a= -9.8 m/s^2 (acceleration due to gravity)
t= 4 s (time)
v[tex]_0[/tex]= 20 m/s (initial speed)
when you solve, the final velocity is -19.2 m/s, so the velocity is negative (the object is on its way down).
