## Physics: Principles with Applications (7th Edition)

Call “forward” the positive direction. Let J denote the jogger, B the boat, and W the water. The pair “JB”, for example, represents the Jogger’s motion relative to the Boat. $$\vec{v_{JW}} = \vec{v_{JB}} + \vec{v_{BW}} = 2.0 m/s + 8.5 m/s = 10.5 m/s.$$ Later, for the jogger moving toward the stern: $$\vec{v_{JW}} = \vec{v_{JB}} + \vec{v_{BW}} = (-2.0 m/s) + 8.5 m/s = 6.5 m/s.$$