Question 1159484


 {{{d = rt - 5t^2}}}

given: an initial velocity of {{{r=9}}} meters per second

 the potato be back at the level of the launcher when {{{d=0}}}

{{{0= 9t - 5t^2}}}...factor

{{{0= (9 - 5t)t}}}

solutions:

{{{t=0}}}->disregard (it’s time  before launching)

or

{{{9 - 5t=0}}}

{{{9=5t}}}

{{{t=9/5}}}

{{{t=1.8}}} 

the potato will be back at the level of the launcher  in {{{1.8}}} seconds