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Unformatted text preview: Solutions for Problems assigned for Chapt 1. 1-2C On a downhill road the potential energy of the bicyclist is being converted to kinetic energy, and thus the bicyclist picks up speed. There is no creation of energy, and thus no violation of the conservation of energy principle. 1-4C A car going uphill without the engine running would increase the energy of the car, and thus it would be a violation of the first law of thermodynamics. Therefore, this cannot happen. Using a level meter (a device with an air bubble between two marks of a horizontal water tube) it can shown that the road that looks uphill to the eye is actually downhill. 1-9 The interior dimensions of a room are given. The mass and weight of the air in the room are to be determined. Assumptions The density of air is constant throughout the room. Properties The density of air is given to be = 1.16 kg/m 3 . Analysis The mass of the air in the room is kg 334.1 = = = ) m 8 6 )(6 kg/m (1.16 3 3 V m Thus, N 3277 = = = 2 2 m/s kg 1 N 1 ) m/s kg)(9.81 (334.1 mg W 1-15 Gravitational acceleration g and thus the weight of bodies decreases with increasing elevation. The percent reduction in the weight of an airplane cruising at 13,000 m is to be determined. Properties The gravitational acceleration g is given to be 9.807 m/s 2 at sea level and 9.767 m/s 2 at an altitude of 13,000 m. Analysis Weight is proportional to the gravitational acceleration g , and thus the percent reduction in weight is equivalent to the percent reduction in the gravitational acceleration, which is determined from 0.41% = = = = 100 807 . 9 767 . 9 807 . 9 100 in %Reduction in weight %Reduction g g g Therefore, the airplane and the people in it will weight 0.41% less at 13,000 m altitude....
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- Fall '09