Answers to homework problems: Chapter 3. 13) Neglecting gravity and air resistance: a) v_y = 130000/3600 m/s sin(37) --> y = v_y * t = 65.2 m b) v_x = 130000/3600 m/s cos(37) --> x = v_x * t = 86.5 m 47) a) 60 km/h - 20 km/h = 40 km/h b) 60 km/h - 20 km/h - 90 km/h = -50 km/h 50) boat velocity perpendicular to the river v_y = 3.5 m/s * cos(40) = 2.68 m/s crossing time t = 200 m / 2.68 m/s = 74.6 s boat velocity upstream v_x = 3.5 m/s * sin(40) = 2.25 m/s displacement d = (v_x - v_current) * t --> v_current = - d/t + v_x = 1.91 m/s 63) a) y = v_y * t -1/2 g * t^2. Initial velocity v_y = 0. --> t = sqrt( 1m * 2/g) = 0.45 s b) x = v_x * t = 1.25 m/s * 0.45 s = 0.56 m