Newton's first law is applicable

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

Three forces given by vectors $2 \hat{i} + 2 \hat{j}$,$2 \hat{i} - 2 \hat{j}$,and $-4 \hat{i}$ are acting together on a point object at rest. The object moves along the direction:

What does the mass of a body measure?

$A$ man getting down from a running bus falls forward because:

$A$ 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?