Question

A rocket is fired vertically up from the ground. It moves upwards with a constant acceleration $10\, m / s ^{2}$ for $30$ seconds after which the fuel is consumed. After what time (in $\sec$) from the instant of firing, the rocket will attain the maximum height? Take $g=10\, m / s ^{2}$

Answer 1

Time taken to attain max. velocity is $t$
$V =0+ t$ ...(1)
time taken to attain maximum height
$(V=0) t'$
$0= V -a t ' ; V = at =a t ' ; t = t '$
Total time to attain maximum height
$T = t + t '=2 t =2 \times 30\, \sec =60\, \sec$.