Baseball: Rising and Falling speed

[Trizz]

Homework Statement

A baseball is seen to pass upward by a window 28 m above the street with a vertical speed of 8 m/s. The ball was thrown from the street.

(a) What was its initial speed?
(b) What altitude does it reach?
(c) How long after it was thrown did it pass the window?
(d) After how many more seconds does it reach the street again?

Homework Equations

Vf = Vi + at
Vf^2 = Vi^2 + 2ad
d = Vi(t) + (.5)(a)(t)^2
t = Vf/a or Vf-Vi/a

The Attempt at a Solution

So far I've only attempted a and c because I don't know how to go aout solving b or d.

For a, I used the Vf^2 formula and changed it to equal Vi^2. So I had:

2(a)(d) - Vf^2 = Vi^2 and with that I got 2(9.8)(28) - (8)^2 = Vi^2 and got 22

I believe the problem may be with acceleration. Is it 9.8 when thrown uo, or only during free fall?


For c, I took the answer i got from a, Vi = 22, and plugged it into the time equation. I did 8 - 22 / 9.8 to get 1.4 seconds.

 

[member 553083]

I'm not sure if my answers for a and c are correct. If someone could help me with b and d, I'd really appreciate it.