A rocket moves upward, starting from rest

with an acceleration of 28.1 m/s2
for 5.21 s.
It runs out of fuel at the end of the 5.21 s, but
does not stop.
How high does it rise above the ground?

1 answer

Assume full mass of rocket is m, before igniting.

If one assumes the mass of the rocket does not change when burning fuel..

nettrust*time=mass*velocityatburnout
ma*time=m*vburnout
28.1*5.21=vburnout.

how high has it went at burnout?
Vf=2ah where vf=burnout velocity.
solve for h.

Now how much higher does it go?
Vf2^2=Vburnout^2-2gh'
solve for h', add it to h.

vf2=0 at top