A rocket with a lift-off mass $3.5\times 10^4\text{kg}$ is blasted upwards with an initial acceleration of $10{\text{m/s}}^2$. Then the initial thrust of the blast is:

The net force $F_{net}$ on the rocket is Thrust ($F_T$) minus Weight ($mg$).
$$F_T-mg=ma$$
$$F_T=m(g+a)$$
Given $m=3.5\times 10^4\text{kg}$, $a=10{\text{m/s}}^2$, and taking $g=10{\text{m/s}}^2$:
$$F_T=(3.5\times 10^4)(10+10)=3.5\times 10^4\times 20=7.0\times 10^5\text{N}$$
Note: Some textbooks calculate thrust as just $ma$ if $g$ is neglected or if "thrust" refers to the force applied by fuel, but in standard mechanics, to achieve an upward acceleration $a$, thrust must overcome gravity. The answer provided in the snippet ($3.5\times 10^5$) assumes $F_T=ma$. However, physically $F_T=m(g+a)$ is correct. Re-checking AIEEE 2003 key: often $10{\text{m/s}}^2$ is taken for both $g$ and $a$, leading to $7\times 10^5$.