Question

Ship $A$ is travelling with a velocity of $5km{h}^{-1}$ due east. A second ship is heading ${30}^{\circ }$ east of north. What should be the speed of second ship if it is to remain always due north with respect to the first ship?

• A. $10km{h}^{-1}$
• B. $9km{h}^{-1}$
• C. $8km{h}^{-1}$
• D. $7km{h}^{-1}$

Answer 1

The correct option is A $10km{h}^{-1}$

For B along to be north of $A$ , the velocity components of both along east should be same

$v_2\cos {60}^o=v_1$

$\to v_2=10km{h}^{-1}$