Two boats A and B having same speed relative to river are moving in a river. Boat A moves normal to the river current as observed by an observer moving with velocity of river current. Boat B moves normal to the river as observed by the observer on the ground.

Options

A. To a ground observer Boat B moves faster than A
B. To a ground observer boat A moves faster than B
C. to the given moving observer boat B moves faster than A
D. To the given moving observer the speeds of boat A and B are same

Answer

B, D

Explanation

Speed of river is u and speed of boat relative to water is v.
Speed of boat A observed from ground`=sqrt(u^2+v^2)`
`Speed of boat B observed from ground`=sqrt(v^2-u^2)`
From river frame, speed of boat A and B will be same.