If a 16 kg object is moving with a constant velocity of 10 m/s and a force of 4 N is applied to it in the opposite direction of its motion, how much time will it take for the object to come to a complete stop?

Given:
Force, F = 4 N
Initial velocity, u = 10 m/s
Mass, m = 16 kg
We know, the body comes to rest.
Therefore, the final velocity, v = 0 m/s

In order to find time, first we need to find the acceleration.
According to Newton's second law of motion,
F = Mass x Acceleration
$\therefore$Acceleration = $-\frac{4}{16}=-\frac{1}{4}\mathrm{m}/{\mathrm{s}}^2$
Acceleration must be negative as the body is coming to rest.

We know that acceleration is given by:
Acceleration = $\frac{\mathrm{v}-\mathrm{u}}{\mathrm{t}}$
Time, t = $\frac{0-10}{-{\displaystyle \raisebox{1ex}{$1$}\!\left/ \!\raisebox{-1ex}{$4$}\right.}}= \frac{4 \mathrm{x} 10}{1}= 40$ s

Therefore, the body will take 40 seconds to come to rest.