## Physics for Scientists and Engineers: A Strategic Approach with Modern Physics (4th Edition)

(a) We can find the time it takes to row across the river. $t = \frac{d_n}{v_n} = \frac{100~m}{2.0~m/s}$ $t = 50~s$ We can find the distance to the east that the river will push Mary's boat in this time. $d_{e} = v_e~t = (1.0~m/s)(50~s)$ $d_{e} = 50~m$ Mary will be 50 meters from her intended landing spot. (b) We can find the boat's speed with respect to the shore. $v = \sqrt{(v_n)^2+(v_e)^2}$ $v = \sqrt{(2.0~m/s)^2+(1.0~m/s)^2}$ $v = 2.2~m/s$