Question

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

• A. $1.75 \times 10^5 \, N$
• B. $7.0 \times 10^5 \, N$
• C. $14 .0 \times 10^5 \, N$
• D. $3.5 \times 10^5 \, N$

Answer 1

Answer: (B)

$7.0 \times 10^5 \, N$

Answer 2

Net upthrust = Weight + Blasted force
$U = mg + 3.5 \times {10^4 \times 10\, m \, s^{-2}}$
$U = {3.5 \times 10^4 \times 10\, m \, s^{-1} + 3.5 \times 10^4 \times 10 \, m\, s^{-2}}$
$U ={ 7.0 \times 10^5 \, N}$