Question

A ship of mass $3\times {10}^7$ kg, initially at rest, is pulled by a force of $5\times {10}^{4}N$ through a distance of 3 m. Assuming that the resistance due to water is negligible, the speed of the ship is

• A. $1.5m/s$
• B. $60m/s$
• C. $0.1m/s$
• D. $5m/s$

Answer 1

The correct option is C $0.1m/s$

$\text{Step 1: Acceleration of the ship, a}$

Applying Newton's law,

$F=ma$

$\Rightarrow a=\frac{F}{m}=\frac{5\times {10}^4}{3\times {10}^7}=\frac{5}{3}\times {10}^{-3}m/s^2$

$\text{Step 2: Final speed of the ship}$

Using $3^{rd}$ equation of motion,

$v^2-u^2=2as$

$\Rightarrow v^2-0^2=2\times \frac{5}{3}\times {10}^{-3}m/s^2\times 3m$

$\Rightarrow v^2={10}^{-2}$

$\Rightarrow v=0.1m/s$

Hence, option $\left(C\right)$ is correct.