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mt1sol_08

# mt1sol_08 - Phyiscs 9A-A Midterm 1 Solutions...

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F N mg f tires f drag v a t a c F T mg F T wÛg Phy 9A-A, Midterm 1 Solutions, Page 1 of 2 4/25/08 F tires f drag v v w v bÛg v bÛw oe Phyiscs 9A-A Midterm 1 Solutions Cole [1] a) radians/second, b) none, c) acceleration opposite to v , d) Both land at the same time, e) both of the above, f) cos oe î + sin oe , g) both, h) GMm r 2 ˆ r , i) false, j) angular speed. [2] a) (10 pts) If you don't know the circumference of the earth you can estimate it. Because the day is 24 hrs, there are 24 time zones. The USA is about 3 complete zones wide (0.5ªeastern +midwest+mountain+0.5ªPacific). The USA is 3000 mi wide õ 1000 mi /time zone õ C í 24,000 mi. r e = C 2 π = 24000 mi ( ) 1600m/mi ( ) 2 3 ( ) = 6.4 ª 10 6 m. b) (10 pts) M =®V = density ª volume = ρ 4 π 3 R 3 π  and 3 are approximately the same M ρ 4 R 3 . We need to estimate the density and the radius of the earth. Water has a density of 1000 kg/m 3 and iron is 7 times denser than water. Earth has a large iron core so estimate ® í 6000 kg/m 3 . M 6000 kg/m 3 ( ) 4 6.4 × 10 6 m ( ) 3 = 6.3 ª 10 24 kg. actual is 5.98

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mt1sol_08 - Phyiscs 9A-A Midterm 1 Solutions...

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