Arann launches a rock into the air such that it rises 20.0 m in the first third (time wise) of its ascent to maximum height.

Determine the rock's maximum height and launch speed.
Determine the time(s) at which the ball is at a height of 10m.
PLEASE HELP

3 answers

find the first third time
20=1/2 g t^2 + vi*t
or 4.9t^2-vi*t+20=0
and
vf=vi+gt
at the top 0=vi-9.8*3t

ok, then t=vi/(9.8*3)
Put that in the first equation, solve for vi.

Then, you can solve all else.
^^ bobpursley
What formula did you use? Could you repost it using v1 and v2 as variables?
vi is launch speed.
vf is the vertical velocity at the top,zero.