The mysterious sliding stones . Along the remoteRacetrack Playa in Death Valley,
ID: 1762864 • Letter: T
Question
The mysterious sliding stones. Along the remoteRacetrack Playa in Death Valley, California, stones sometimes gougeout prominent trails in the desert floor, as if they had beenmigrating (Fig. 6-19). For years curiosity mounted about why thestones moved. One explanation was that strong winds during theoccasional rainstorms would drag the rough stones over groundsoftened by rain. When the desert dried out, the trails behind thestones were hard-baked in place. According to measurements, thecoefficient of kinetic friction between the stones and the wetplaya ground is about 0.647. What horizontal force is needed on astone of typical mass 21 kg to maintain the stone's motion once agust has started it moving?
Explanation / Answer
=.647 m=21 g=9.8 F= mg=133.15