The proper length of spaceship A is 60.0 m and the proper length of spaceship B is 120.0 m. The proper mass of spaceship A is 15 000 kg. An observer on earth watches the two spaceships fly past at a constant speed and determines that they have the same length. If the speed of the slower spaceship is 0.70c, find the length of spaceship A, relative to an observer on earth. (3 marks) the speed of spaceship B, relative to an observer on earth. (3 marks) the mass of spaceship A, relative to an observer on earth

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