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I've been working on this problem for a while and our book doesn't have a solutions manual. It has 4 parts to it and I've solved 2 already, (I think) and the last 2 are just getting to me.

-A ball is thrown from the top of a building and is given an initial velocity of 30 m.s upward. The building is 60M high.

1). Determine the time needed for the stone to reach its max height

vf=at+vi

-30=-10t, t=3

2). Maximum height?

d= .5AT^s +viT

.5(-10)(3)^2+30(3)

= -5(9)+ 90

=15M

Velocity of the ball just before it hits the ground and the total time the ball is in the air?

What i did was

x=voT +.5AT^2 and solved for T but that cant be right because the answer i get is less that 7 seconds, and question following this says find the velocity and position at 7 sec. so it has to be AT LEAST 7 sec.

then i substituted that t for v=vo+at. so really, the 4th question is not the problem it's the 3rd.

Any help is appreciated