According to Einstein’s first postulate about the special theory of relativity, which best explains why a person feels like he or she is sitting still on a train that is moving at a constant speed of 60 miles per hour?

Einstein’s first postulate says the laws of physics are the same in all inertial reference frames, including one moving at a constant speed. Inside the train, the person uses the train as their reference frame, so they and the seat are at rest relative to each other and feel still. The correct choice is “The reference frame of the person is inside the train.”

AI-written and checked against the verified answer.