Question

You are planning to cross a river by a small motor boat. The speed of your boat is v = 2.71 m/s in still water. At which angle with respect to the perpendicular crossing direction do you need to aim your boat, if you want to cross the river in the shortest possible distance? The speed of the water is 1.19 m/s. 26.0 deg You are correct. Your receipt no. is 155-6363 Previous Tries After a day of very heavy raining the level of the river rises up, and the speed of the water increases to 4.75 m/s. At which angle with respect to the perpendicular direction do you need to aim your boat this time, if you want to cross the river in the shortest possible distance? 34.8 deg Submit Answer Incorrect. Tries 9/12 Previous Tries

Answer 1

2.71 (@ Velocity of the boat - en mis 27 ! Vo = 1.19 mb Velocity of the River - 1.19 m/s Now the shortest path to cross the river i the crossing it perpendicularly. If it crosses the river perpendicularly, then it's velocity's component in the direction of river must be of equal to river How velocity an SHE vu V = Vsind —). To cross it perpendicularly (11- ي = x usind = Vu 2-71 sind = 1:19 sind = 0.439 . 8 = 26-04 An (6) Now due heavy rais velocity of river increases to y = 4.75 m/s . Put cross the nuer in the shortest possible distance r direction of should be perpendicular, so now, put the value of Vo in eqlii Vy = 4.75 V sino = 4.75 sing = 4,25 = 1-75 since the value of sino must lie in the range of [-t, d]. so to cross it perpendicularly ů impossible. Now to calculate other shortest possible distance, we need the width of the river. 2,71 UIO