Suppose a Person Is in a Jet Airliner Traveling at a Constant

Multiple Choice

Suppose a person is in a jet airliner traveling at a constant speed of 400 km/h in a constant direction. All windows are blocked, so they cannot see outside, and there are no vibrations from the engines. What experiment can be done to determine that they are in fact moving?

A) Suspend a ball by a thread from the ceiling and measure the angle the thread makes with the vertical.
B) None-all experiments will give the same results that one would get when at rest on the ground.
C) Measure the speed of a sound wave traveling up the aisle (toward the nose of the aircraft) and another traveling down toward the tail, and calculate the difference between the two results.
D) Drop a small rock and measure the distance it moves backward down the aisle as it falls.