- ✓$36\ km, 1\ min$
- B$6\ km, 1\ min$
- C$36\ km, 1\ hour$
- D$36\ km, 1\ sec$
and velocity acquired by it will be $v=10 \times 60=600 m / s \ldots(i i)$
Now, after $1 \mathrm{min}$ the rocket moves vetically up with velocity of $600 \mathrm{m} / \mathrm{s}$ and acceleration due to gravity opposes its motion. So, it will go to a height $h_{2}$ till its velocity becomes zero such that $0=(600)^{2}-2 g h_{2}$
or $h_{2}=18000 \mathrm{m}\left[\mathrm{as} g=10 \mathrm{m} / \mathrm{s}^{2}\right] \ldots .(\text { iii })$
$=18 k m$
So, from Eqs. (i) and (iii) the maximum height reached by the rocket from the ground $h=h_{1}+h_{2}=18+18=36 k m$
As after burning of fuel the initial velocity from Eq. ( i. ) is $600 \mathrm{m} / \mathrm{s}$ and gravity opposes the motion of rocket, so the time taken by it to reach the maximum height (for which $v=0$ ). $0=600-g t$
or $t=60 s$
i.e. after finishing fuel the further goes up for $60\; s$, or $1 \mathrm{min}$.
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