Final answer:
A car moving at constant velocity can have an inertial frame attached to it, whereas a car that is accelerating and an elevator in free fall cannot, because they are not maintaining a constant velocity without the influence of an external force.
Step-by-step explanation:
Taking a frame attached to Earth as inertial, which of the following objects cannot have inertial frames attached to them, and which are inertial reference frames?
- (a) A car moving at constant velocity is an inertial reference frame because it is moving at a constant speed in a straight line without external forces causing acceleration.
- (b) A car that is accelerating cannot have an inertial frame attached to it because this implies a change in velocity, which means it is not moving at a constant speed or in a straight line without being acted on by an outside force.
- (c) An elevator in free fall cannot have an inertial frame attached to it as well. While it may seem to be moving at a constant velocity to someone inside, it is actually accelerating due to gravity, which is an external force.
An inertial reference frame is defined as one in which an object at rest or in motion with a constant velocity stays that way unless acted on by an external force. Therefore, an object in an inertial frame will not be accelerating, rotating, or undergoing any non-uniform motion.