Correct Answer - A::B
In order that the moving launch is always on the
straight line AB, the components of velocity of the
current and of the launch in the direction
perpendicular to AB should be equal, i.e.
`u sin beta = v sin alpha` ...(i)
`S = AB = (u cos beta + v cos alpha) t_1` ...(ii)
Further `BA= (u cos beta - v cos alpha) t_2` ...(iii)
`t_1 + t_2 = t` ...(iv)
Solving these equations after proper substitution,
we get
`u= 8 m//s and beta=12^@`