Answer:
+12 m/s
Explanation:
The velocity of an object moving of accelerated motion is given by:
[tex]v(t) = v_0 +at[/tex]
where
v0 is the initial velocity of the object
a is the acceleration
t is the time
In this problem, the rocket starts from rest, so [tex]v_0 =0[/tex]. The acceleration is [tex]a=4 m/s^2[/tex], so the velocity after [tex]t=3 s[/tex] will be
[tex]v(3 s)=0 +(4 m/s^2)(3 s)=+12 m/s[/tex]
