Chapter 3, Problem 61P

(II) A child, who is 45 m from the bank of a river, is being carried helplessly downstream by the river’s swift current of 1.0 m/s. As the child passes a lifeguard on the river’s bank, the lifeguard starts swimming in a straight line until she reaches the child at a point downstream (Fig. 3-50). If the lifeguard can swim at a speed of 2.0 m/s relative to the water, how long does it take her to reach the child? How far downstream does the lifeguard intercept the child?

FIGURE 3-50 Problem 61.