Question

An athlete crosses a 25-m-wide river by swimming perpendicular to the water current at a speed of 0.5 m/s relative to the water. He reaches the opposite side at a distance 40 m downstream from his starting point. How fast is the water in the river flowing with respect to the ground? What is the speed of the swimmer with respect to a friend at rest on the ground?

$v_{wg} = 0.80 \textrm{ m/s}$, $v_{sg} = 0.94 \textrm{ m/s}$

Solution Video