Mechanics M1
posted by Sunder .
A girl swims across a river. When she swims in still water, she swims at 1.25 m/s, the river flows parallel to its banks at v m/s. The girl aims to swim upstream at angle θ degree to the river bank so that her resultant velocity of 1 m/s is along AB, perpendicular to the river bank.
Find V and θ

velocity downstream is zero (she swims directly across)
1.25cosTheta=1 solve for theta
1.25sinTheta=V solve for V 
is the same thing if in problem say
"at angle θ degrees parallel to the river bank"