19 “Suppose that, while lying on abeach near the edquator watch-
ing 了e 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 五 三1.70 m, and stop 了he watch when the top of the Sun
agaln disappears. 本 the elapsed time 18/ 三 11.1 s, what is the radius
7 OfEEarth?
ae
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