Homework Help: Solve it using energy conservation?

1. Jan 21, 2010

majormuss

1. The problem statement, all variables and given/known data
I just came across this question and i think its giving me a real hard time.
This is part of a bigger question so I'll provide the other statements below
7 The maximum height reached by the ball is
approximately
(1) 1.2 m (3) 4.9 m
(2) 2.5 m (4) 8.5 m

2. Relevant equations
t=1 s and therefore half way is 0.50s
V(i)=8.9m/s
angle is 35 degrees
Viy= 4.9m/s

3. The attempt at a solution
First of all, why is it that I can't use certain formulas in Solving some motion problems even though everything seems to work ok. I tried using this formula....d=V(i)t +1/2at^2... but my answer turns out wrong. and this one rather gives me the answer...Vf^2=Vi^2 + 2ad.......why is that?

Last edited by a moderator: Jul 18, 2014
2. Jan 21, 2010

ekkilop

Re: Kinematics

Since you know the initial velocity, why not try to solve it using energy conservation?

3. Jan 21, 2010

tiny-tim

Hi majormuss!

(try using the X2 tag just above the Reply box )
All the standard constant acceleration formulas will work.

I expect you got t = 0.5 s wrong … where did that come from?