Question

An object is placed far away from all the objects that can exert force on it. A frame of reference is constructed by taking the origin and axes is fixed in this object. Will the frame be necessarily inertial?

Answer 1

Since the origin and the axes are fixed in the object, the frame of reference will always move with it. The acceleration of the object with reference to this frame will always be zero. Now the sum of forces on the object will also be zero because no other object can exert force on it. So in this frame of reference always a=0 for F=0. So it is an inertial frame.