A river has a steady speed of 0.500 m/s. A student swims upstream a distance of

Question

A river has a steady speed of 0.500 m/s. A student swims upstream a distance of 1.00 km and swims back to the starting point. If the student can swim at a speed of 1.20 m/s in still water, how long does the trip take (swimming up and down in the current)? Your response differs from the correct answer by more than 10%. Double check your calculations. s If the water were still, by how much would the trip be longer or shorter? (Give a negative answer for a shorter trip.) The response you submitted has the wrong sign. s Need Help? Talk to a Tuto

Explanation / Answer

The student swims 1.20 m/s in still water

can swim = 1.20 - 0.500 = 0.7 m/s [upstream]

can swim = 1.20 + 0.500 = 1.7 m/s [downstream]

Going upstream , t = d / v = 1000 / 0.7 = 1428.57 s = 23.81 min

Going downstream, t = d / v = 1000 / 1.7 = 588.24 s = 9.80 min

total trip = 1428.57 + 588.24 = 2016.8 s = 33.61 min

If the water were still, the trip would take = 2000 / 1.2

If the water were still, the trip would take = 1666.67 s = 27.78 min

Difference = 1666.67 - 2016.8 = -350 s

In still water, so the trip would have been shorter by 350 sec

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