by COLM along `x` axis:
`200M=400xx(M)/(4)cos60^(@)+(3M)/(4)Vcostheta`
`(3)/(4)vcostheta=150" "rArrvcostheta=200`...(i)
by COLM along `y` axis:
`0=400(M)/(4)sin60^(@)-(3M)/(4)Vsintheta`
`3vsintheta=(400sqrt3)/(2)`
`vsintheta=(200)/(sqrt3)`...(ii)
(ii)/(i) given
`tantheta=(1)/(sqrt3)`
`rArr" "theta=30^(@)`
`rArr" "v=(400)/(sqrt3)m//s`