英语翻译
An elevator without a ceiling is ascending with a constant speed of 10 m/s.A boy on the elevator throws a ball directly upward,from a height of 2.0 m above the elevator floor,just as the elevator floor is 28 m above the ground.The initial speed of the ball is 20 m/s.(a) What is the maximum height attained by the ball?(b) How long does it take the ball to return to the elevator
floor?