Quick Reference Frames Problem. Soon

[jollyrancher9]

A ferry cross a river of width d. The speed of the boat is v relative to the water, and the speed of the tidal current is w parallel to the riverbanks. The ferry landing points are directly opposite each other on each side of the river. How long does the shortest return trip take?

My attempt: vector v and vector w add to form vector v+w, which is directionally a straight line between the 2 ferry landing points. Then, (v+w) = d/t, and t = d/(v+w), where d, v and w are all vectors. Is this correct? The answer seems too simplistic.

Thanks to everyone for taking the time to look at this. Your help is much appreciated!


jollyrancher99

 

[housemartin]

Hello!
v and w are not parallel. Ferry crosses river - its velocity is perpendicular to the riverbank and river flows parallel to the riverbanks. So you can't write t = d/(v+w). For ferry to travel perpendicularly to the riverbank, component of v along riverbank must cancel velocity of the tidal current w. Guess this helps.