일반물리학 1 — Measurement: Problem 19

19 Suppose that, while lying on a beach near the equator watching the Sun set over a calm ocean, you start a stopwatch just as the top of the Sun disappears. You then stand, elevating your eyes by a height \(H = 1.70 \text{ m}\), and stop the watch when the top of the Sun again disappears. If the elapsed time is \(t = 11.1 \text{ s}\), what is the radius \(r\) of Earth?