Question

Resultant force acting on a moving body is zero, then
(1) its path must be straight line as seen from an inertial frame
(2) its path may be curved as seen from a non inertial frame
(3) its path must be straight line whether the frame is inertial or non inertial
(4) both 1 and 2 are correct

Answer 1

Resultant force acting on a moving body is zero, then (1) its path must be straight line as seen from an inertial frame.

• If the force on a moving body is zero, then its acceleration and other elements will also be zero. In such a condition the frame will be an inertial frame.
• If on a body, there is no force, then it will continually rest or travel at a constant velocity in a straight line.