Hey,

I have this problem in physics which I know the answer to (answers are in the back), but I'm getting a different answer. At this point I'm thinking the back of the book is wrong

The question:

Object A is dropped by an Object B that is rising steadily at .5 m/s.

a) After 2.5 s, what is the velocity of Object A?
b) How far below Object B is Object A after 2.5 s?


solution to a:

vf = vi + at
vf = .5 + (-9.8 m/s)(2.5 s)
vf = -24 m/s (Correct answer)


solution to b:

x = (.5 m/s)(2.5 s) + .5(-9.8 m/s)(2.5 s)^2
x = -29.375 (wrong answer)

The correct answer should be 31 m, but how in the world did they get that? I've tried many of the formulas I have and still come up with the same answer.


Can anyone shed some light on part B?