# Determine Earth's radius with stopwatch at sunset [closed]

This question appeared on Bangladesh physics Olympiad 2014, Sylhet, Bangladesh for students of class 9 and 10.

Suppose that, while lying on the 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, and fitting your eyes by a height $$H=1.70\,\mathrm m$$, and stop the watch when the top of the sun again disappears. If the elapsed time is $$T=574\,\mathrm s$$, what is the radius of the Earth?