Question

Which describes an inertial frame of reference?

Answer 1

Newton's first law is valid within the frame describes an inertial frame of reference.

Answer: Option A

Explanation:

A frame of reference is defined as the system in which the motion or state of any object is observed and stated with respect to the set of space and time, observer or any other object or environment, either moving or at rest.  

The two types of frame of references to be studied by us are the Inertial and non-inertial.  An inertial reference frame is defined in that a body is either at rest or moves with a constant speed or velocity if there is no external force exerted upon it i.e. the objects are either rest or move at a same velocity.

Since it’s quite clear through the definition that an inertial frame of reference obeys Newton’s first law of motion, we have the first option as the perfect answer.

Answer 2

No forces are exerted within the frame