Mary applies a force of 75 N to push a box with an acceleration of 0.57 m/s. When she increases the pushing force to 81 N, the box's acceleration changes to 0.87 m/s . There is a constant friction force present between the floor and the box. (a) What is the mass of the box in kilograms? kg (b) What is the coefficient of kinetic friction between the floor and the box?A rotating space station is said to create "artificial gravity"-a loosely-defined term used for an acceleration that would be crudely similar to gravity. The outer wall of the rotating space station would become a floor for the astronauts, and centripetal acceleration supplied by the floor would allow astronauts to exercise and maintain muscle and bone strength more naturally than in non-rotating space environments. If the space station is 250 m in diameter, what angular velocity would produce an "artificial gravity" of 9.80 m/s2 at the rim? rpm