Suppose that, while lying on a beach near the equator of a far-off planet 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 = 1.63 m, and stop the watch when the top of the sun again disappears. if the elapsed time is t = 10.1 s, what is the radius r of the planet to two significant figures? notice that duration of a solar day at the far-off planet is the same that is on earth. (hint: see sample problem 1-4.)

You have two photos of a person walking. one shows the person at the corner of third and main streets, the other shows the person at the corner of tenth and main streets. there are lampposts at every corner in this town, and the first picture shows it to be 10: 32: 00 exactly. the second picture shows it to be 10: 49: 30. you know three facts: (1) all of the clocks are synchronized; (2) there are exactly 12 equal-sized blocks per kilometer in this town; and (3) the streets that cross main in this area are numbered consecutively, with no interruptions. what is the person’s average speed in kilometers per hour?