Question

If a ship of mass $4\times {10}^7$ kg initially at rest is pulled by a force of $5\times {10}^4$ N through a distance of $4m$, then the speed of the ship will be (resistance due to water is negligible)

• A. $5m{s}^{-1}$
• B. $1.5m{s}^{-1}$
• C. $60m{s}^{-1}$
• D. $0.1m{s}^{-1}$

Answer 1

Answer: (D)

$0.1m{s}^{-1}$

Work done on the ship: $W=Force\times distance=5\times {10}^4\times 4=20\times {10}^4$
Work done $=$ Change in KE of ship
$\Rightarrow \frac{1}{2}m{v}^2-0=20\times {10}^4$
$\Rightarrow v=\sqrt{\frac{2\times 20\times {10}^4}{4\times {10}^7}}=0.1m/s$