A rocket is fired vertically with an acceleration of 16m/s^2. After time T, the rocket's engine runs out of fuel and it begins to fall freely. The maximum height of the rocket is 940m, what is the minimum value of T?

Answer 1

the distance traveled by the rocket in T seconds with the acceleration 16m/s.s is=940m
velocity=16*Tm/s=16Tm/s
during T seconds the rocket moved upward with velocity 16T m/s and downward accelaration due to gravity till its velocity becomes zero.
0=(16T*16T)-2gh2
= 256T.T-2*10h2
h2=256T.T/20
now,256T.T+160T.T/20=940
or,416T.T=940
or,T.T= 940/416=2.25
or, T=1.5s