physics
posted by alk .
An elevator without a ceiling is ascending with a constant speed of 10m/s. A boy on the elevator shoots a ball directly upward, from a height of 2.0m above the elevator floor, just as the elevator floor is 28m above the ground. The initial speed of the ball with respect to the elevator is 20m/s.
a) How long does the ball take to return to the elevator floor?

The elevator is not accelerating. Therefore you and the ball can not feel how fast it is going. The problem is just the same as if you did the experiment on the ground. The 10 m/s is irrelevant and the 28 m above ground is irrelevant and the problem is
h = 0 = 2 + 20 t  (1/2)(9.8) t^2
solve the quadratic for t 
the answer lies in the book....
peace and wisdom 
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