Question

A rocket with a lift-off mass $2\times {10}^{4}kg$ is blasted upwards with an initial acceleration of $5m{s}^{-2}$. The initial thrust of the blast is (Take $g=10m{s}^{-2}$)

• A. $2\times {10}^{5}N$
• B. $3\times {10}^{5}N$
• C. $4\times {10}^{5}N$
• D. $5\times {10}^{5}N$

Answer 1

The correct option is B $3\times {10}^{5}N$

Here, m= $2\ast {10}^{4}kg$
Initial acceleration, $a=5m{s}^{-2}$
Initial thrust = upthrust required to impart acceleration a+ upthrust required to overcome gravitational pull
$\therefore F=m(a+g)=(2\times {10}^{4}kg)(5+10)m{s}^{-2}=3\times {10}^{5}N$