Question

A ship is travelling due east at $10\text{km/hr}$. Another ship heading ${30}^{\circ }$ east of north is always due north from the first ship. The speed of the second ship in $\text{km/hr}$ is

• A. $20\sqrt{2}$
• B. $20\sqrt{\frac{3}{2}}$
• C. $20$
• D. $\frac{20}{\sqrt{2}}$

Answer 1

The correct option is C $20$

The condition of both the ships are shown in figure $\left(A\right)$ and figure $\left(B\right)$ shows the condition of ship $2$ when it is always due north to the ship $1$.

So, east component of both ships must be same.
$\therefore$ $v_{s2}\sin {30}^{\circ }=v_{s1}$
$v_{s2}=\frac{10}{\frac{1}{2}}=20km/hr$