Newton's first law is applicable only in _.

Explanation

Newton's first law of motion is applicable only in inertial frames of reference. An inertial frame of reference is a frame of reference in which Newton's laws of motion are valid. In an inertial frame of reference, an object will remain at rest or in motion at a constant velocity unless acted upon by a force. The Earth is not an inertial frame of reference because it is rotating around the Sun. This rotation causes the Earth to experience a centrifugal force, which is a force that pushes objects away from the center of rotation. This force is what causes objects to move in a curved path around the Earth. However, the Earth's rotation is very slow, so the centrifugal force is very small. For most purposes, the Earth can be treated as an inertial frame of reference.