Question

A rocket has an initial mass of $20 \times 10 ^ { 3 } \mathrm {~kg}$ . If it is to blast off with an initial acceleration of $4 m s ^ { - 2 }$ , the initial thrust needed is $\left( g \cong 10 m s ^ { - 2 } \right)$

• A. $6 \times 10 ^ { 4 } N$
• B. $28 \times 10 ^ { 4 } N$
• C. $20 \times 10 ^ { 4 } N$
• D. $12 \times 10 ^ { 4 } N$

Answer 1

Answer: (B)

$28 \times 10 ^ { 4 } N$

Answer 2

$F = m ( g + a ) = 20 \times 10 ^ { 3 } \times ( 10 + 4 ) = 28 \times 10 ^ { 4 } \mathrm {~N}$