When a body is at rest or in uniform motion,no force acts on it. Is this statement true or false?

Newton's first law is applicable

Which one of the following persons is in an inertial frame of reference?

$A$ particle is moving with a constant speed along a straight line path. $A$ force is not required to

$A$ stone tied to the end of a string is whirled in a circular path. Why does the stone move in the direction of the tangent at that point when the string breaks?

$A$ trolley of mass $300 \; kg$ carrying a sandbag of $25 \; kg$ is moving uniformly with a speed of $27 \; km/h$ on a frictionless track. After a while,sand starts leaking out of a hole on the floor of the trolley at the rate of $0.05 \; kg \cdot s^{-1}$. What is the speed (in $km/h$) of the trolley after the entire sandbag is empty?