The statement ''acceleration is zero if and only if the net force is zero'' is valid in .

The net force acting is not zero on

The net force acting is not zero on

In which of the following cases the net force is zero?

In which of the following cases the net force is zero .

a) In a frame of reference S( though the net force is zero, the net acceleration is not zero. b) In a frame of reference S_2 though the net force is not zero, the net acceleration is zero. c) In a frame of reference S_3 the net acceleration is zero whenever the net force is zero.

a) In a frame of reference S_1 ( though the net force is zero, the net acceleration is not zero. b) In a frame of reference S_2 though the net force is not zero, the net acceleration is zero. c) In a frame of reference S_3 the net acceleration is zero whenever the net force is zero.

In which of the following cases the net force is not zero ?