Question

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

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

Answer 1

The correct option is C 20

Two components is $v_1$ in north and $v_2$ in east as original speed at $30°⟶$east of north.

So, perpendicular to it, zero velocity.

$v_1\sin 30°=v_2\sin 60°------\left(i\right)$

Also, $v_2=10$

Then, $x=\frac{10}{\sin 30°}=\frac{10}{\left(\frac{1}{2}\right)}=20km/h$