Question

The distance travelled by a moving body is directly proportional to time. Is any external force acting on it?

Answer 1

To find whether external force is acting in the given condition

From the second equation of motion

$S=ut+\frac{1}{2}a{t}^2$

Here, the distance traveled is directly proportional to the time if and only if $a\left(acceleration\right)=0$

If, acceleration is zero that means velocity is constant and no external force is acting.

Hence, no external force is acting, if the distance traveled is directly proportional to time.