Falling through the Earth

摘要

One of the problems inflicted on students in introductory physics courses involves an imaginary hole drilled through the center of the Earth. An observer on the surface drops a rock which proceeds to accelerate down the hole through the center of the Earth. There is a deceleration after the rock passes through the center and it just barely makes it to be momentarily at rest at the other end. The total trip is estimated to be about 42 minutes. Of course, the tube should be a vacuum to remove air resistance to the object's free fall etc. This paper describes angular momentum/energy complications to the problem as it is usually written. There is a chain of recent articles exploring this problem but with no mention of such objections.