Question

A river has a steady speed of 0.370 m/s. A student swims upstream a distance of 1.00 km and swims back to the starting point.

(a) If the student can swim at a speed of 1.30 m/s in still water, how long does the trip take?
s

(b) How much time is required in still water for the same length swim?
s

(c) Intuitively, why does the swim take longer when there is a current?

Answer 1

Speed river

Student Speed in calm water

(a) If the student can swim at a speed of 1.30 m/s in still water, how long does the trip take?
There are two situations.

Case 1

When the student swims upstream of the river.

distance traveled

time is calculated by the following expression (Movement rectilinear uniform)

evaluated numerically

Case 2

Student swimming in direction with the flow of the river

When the student swims upstream of the river.

distance traveled

time is calculated by the following expression (Movement rectilinear uniform)

evaluated numerically

the total time would be the sum of the time in case 1 and case 2

(b) How much time is required in still water for the same length swim?

When the student is swimming in calm water, the speed does not vary all the way

full distance

time is calculated by the following expression (Movement rectilinear uniform)

evaluated numerically

(c) Intuitively, why does the swim take longer when there is a current?

The swimmer speed is affected by the speed of the river, and as it is a long distance causes an increase in the time it takes to do all the full travel. Despite having the second length greater speed.