Question

Two students are canoeing on a river. While heading upstream, they accidentally drop an empty bottle overboard. They then continue paddling for 1.3 hh, reaching a point 1.3 kmkm farther upstream. At this point they realize that the bottle is missing and, driven by ecological awareness, they turn around and head downstream. They catch up with and retrieve the bottle (which has been moving along with the current) 4.6 kmkm downstream from the turn-around point. A) Assuming a constant paddling effort throughout, how fast is the river flowing? B) Assuming a constant paddling effort throughout, how fast is the river flowing?

Answer 1

PART A:

The students are paddling relative to the water, if they paddle in one direction for 1.5 hours then they must paddle in the other direction also for 1.5 hrs to get back to the initial position.

Therefore, the distance that the water has moved in the time (1.3 + 1.3) = 2.6 hrs is by (4.6 - 1.3) km

Hence, the speed of the river is given by:

PART B:

Let V_c be the speed of the canoe.

Since they moved 1.3 km upstream in 1.3 hr we can say:

RESULT:

• Speed of river = 1.3 km/hr
• Speed of the canoe in still water = 2.3 km/hr