A 1000-kg mass on a horizontal friction-free table is accelerated by a string attached to another 1200-kg mass hanging vertically from a pulley. The friction force is equal to half the weight of the mass lying on the table. What is the acceleration of the system of both masses?

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Assume that a person skiing high in the mountains at an altitude of h = 15100 ft takes in the same volume of air with each breath as she does while walking at sea level. determine the ratio of the mass of oxygen inhaled for each breath at this high altitude compared to that at sea level. assume that the air composition (i.e. % of air that is oxygen) is the same at sea level as it is at 15100 ft.