I finding the distance and the time

[Mary0524]

Homework Statement

1. A bottle rocket has an engine that accelerates it upward. Then it coasts to its highest point before returning to the ground. Assuming that the engine creates a net acceleration of 30 m/s2 for 0.5 s, how high does it go, and how long does it take to reach the ground again?

acceleration= 30m/s^2
time=0.5s

Homework Equations

v^2-u^2=2ax

The Attempt at a Solution

0^2-(15m/s)^2=2(-9.8m/s^2)x
-225=-19.6x
-255/-19.6
x=11.48m
to get total height i did 11.48m+3.75m=15.23m

now how do i get velocity for the other question
v=at
v=30m/s^2*0.5s
v=15m/s
does this work?

 

[CWatters]

The acceleration isn't 30m/S^2 on the way down. Nor is the time 0.5 seconds.

 

[OmCheeto]

...
15.23m

That's what I come up with.

now how do i get velocity for the other question
v=at
v=30m/s^2*0.5s
v=15m/s
does this work?

I thought the second part of the question was "find: Total time, from launch to landing"
?