$0.18 \,N ;$ in the direction of motion of the body

Mass of the body, $m=3 \,kg$

Initial speed of the body, $u=2\, m / s$

Final speed of the body, $v=3.5 \,m / s$

Time, $t=25 \,s$

Using the first equation of motion, the acceleration ( $a$ ) produced in the body can

be calculated as: $v=u+a t$

$\therefore a=\frac{v-u}{t}$

$=\frac{3.5-2}{25}=\frac{1.5}{25}=0.06\, m / s ^{2}$

As per Newton's second law of motion, force is given as:

$F=m a$

$=3 \times 0.06=0.18\, N$

since the application of force does not change the direction of the body, the net force acting on the body is in the direction of its motion.