The problem that follow involve straight-line motion. The time t is in seconds unless othe...

The problem that follow involve straight-line motion. The time t is in seconds unless otherwise stated.

Problem

The river flows north at 3 m/s. (Assume that the current is uniform.) What minimum speed must a boat have relative to the water in order to travel in a straight line from point C to point D?How long does it take to make the crossing?

Strategy: Draw a vector diagram showing the relationships of the velocity of the river relative to the earth, the velocity of the boat relative to the river, and the velocity of the boat relative to the earth. See which direction of the velocity of the boat relative to the river causes its magnitude to be a minimum.