Question

A swimmer heading directly across a river that is 200 m wide reaches the opposite bank in 6 min 40 s. During this swim, she is swept downstream 480 m. How fast can she swim in still water?what is the speed of the boat relative to an observer standing on the shore as it crosses the river?What is the speed of the current?

Answer 1

Given the width of the river is w = 200m, the downstream displacement d = 480m and the time taken for it is t = 6min 40s = 400s.

(a) The velocity of the swimmer with respect to the river is given by

So the swimmer can swim 0.5m/s in still water.

(b) The speed of the river current is given by,

So the speed of the river current is 1.2m/s.

c) The resultant speed of the swimmer is,

So the speed of the swimmer relative to an observer standing on the shore as he crosses the river is 1.3m/s.