$A$ constant force acting on a body of mass $3.0 \, kg$ changes its speed from $2.0 \, m/s$ to $3.5 \, m/s$ in $25 \, s$. The direction of the motion of the body remains unchanged. What is the magnitude and direction of the force?

(A) The magnitude of the force is $0.18 \, N$,and its direction is in the direction of the motion of the body.
Given:
Mass of the body,$m = 3.0 \, kg$
Initial speed,$u = 2.0 \, m/s$
Final speed,$v = 3.5 \, m/s$
Time,$t = 25 \, s$
Using the first equation of motion,the acceleration $(a)$ produced in the body is calculated as:
$v = u + at$
$a = \frac{v - u}{t} = \frac{3.5 - 2.0}{25} = \frac{1.5}{25} = 0.06 \, m/s^2$
According to Newton's second law of motion,the force $(F)$ is given by:
$F = m \times a$
$F = 3.0 \, kg \times 0.06 \, m/s^2 = 0.18 \, N$
Since the speed of the body increases and the direction of motion remains unchanged,the force must be acting in the direction of the motion of the body.