Question

A test rocket is fired up from rest. The net acceleration is 20m/s^2 upward and continues for 4.0 seconds, at which time the rocket engines cease firing. What maximum elevation does the rocket reach?

Answer 1

d = 1/2 (a)(t)^2 = 160 m

at rest, Vo = u = 0 m/s

I found the final velocity by using
v = u +at = 0 + (20)(4) = 80 m/s

d = vt
t = 160 m / 80 m/s = 2 s

I might be wrong at this

I know d= Vot - 1/2 (a)(t)^2

By any chance, what textbook are you using?

Answer 2

h=at²/2=20•16/2=160 m