Question

The speed of the boat in still water is 20 $m/s$ and the speed of river flowing due east is 10 $m/s$. If the boat is on the southern end and it has to cross the river along the shortest path, then the angle at which it should move with respect to north is

• A.
  30$°$ west
• B.
  0$°$
• C.
  45$°$ west
• D.
  60$°$ west

Answer 1

The correct option is A

30$°$ west


$\mathrm{Velocity}\mathrm{of}\mathrm{boat}in\mathrm{still}\mathrm{water,}{V}_{SR}=20m/sFlowv\mathrm{elocity}\mathrm{of}river,V_{RG}=10m/s$$\sin \theta =\frac{\left(}{V_{RG}}\sin \theta =\frac{10}{20}\sin \theta =\frac{1}{2}\theta =30°$