Question

In a harbour, the wind is blowing at the speed of 72 km/h and the flag on the mast of a boat anchored in the harbour flutters along the N-E direction. If the boat starts moving at a speed of 51 km/h to the north, what is the direction of the flag on the mast of the boat?

Answer 1

Velocity of the boat, v_b = 51 km/h
Velocity of the wind, v_w = 72 km/h

The flag is fluttering in the north-east direction. It shows that the wind is blowing toward the north-east direction. When the ship begins sailing toward the north, the flag will move along the direction of the relative velocity (v_wb) of the wind with respect to the boat.

The angle between v_w and (–v_b) = 90° + 45°

Angle with respect to the east direction = 45.11° – 45° = 0.11° Hence, the flag will flutter almost due east.