Question

Canoeing a person in a canoe wants to cross a 65-foot-wide river. he begins to paddle straight across the river at 1.2 m/s while a current is flowing perpendicular to the canoe. if the resulting velocity of the canoe is 3.2 m/s, what is the speed of the current to the nearest tenth?

Answer 1

If the water was still, the canoe would cross with a constant velocity of 1.2 m/s. However, the river has a velocity and thus  pulls the canoe in its direction of flow resulting to a higher velocity of 3.2 m/s.

These vectors forms a right-angle triangle with 3.2 m/s as the hypotenuse and 1.2 m/s as the adjacent length. Resolving for the opposite site which represents the river flow velocity, results to:

River speed = Sqrt (3.2^2-1.2^2) = 2.995 m/s
To nearest tenth, river speed = 3 m/s