Maximum height???......Quick Physics Question....?

Question

A rocket moves striaght upward, starting from rest with an acceleration of 29.4m/s^2. It runs out of fuel at the end of 4.00seconds and continues to coast upward, reaching a maximum height before falling back to Earth.

(a.) Find the rocket's velocity and position at the end of 4.00seconds.

(b.) Find the maximum height the rocket reaches.






There was ten parts to this problem and I'm stuck on how todo these to.
Thanks sooo much for the help!!!!

Answer 1

for the first 4 seconds
vy(t)=29.4*t
and
y(t)=.5*29.4*t^2

at t=4, solve for vy and y

vy =117.6 m/s

y= 235.2 m

for the next part of the flight, the rocket will have
vy(t)=117.6-9.81*t

and
y(t)=235.2+117.6*t-.5*9.81*t^2

to find apogee, solve for vy(t)=0

y(12)= 940 m


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