Question

An oarsman can row his boat 3 mph in still water. He sets out on the Illinois River, which flows at 5 mph. We are interested in what an observer on shore measures. 14) When the man heads the boat directly downstream and rows as fast as he can, how fast does the observer on shore see the boat going

Answer 1

The speed from the observer is 8 mph.

Explanation:

When the boat is going downstream with full force, its speed will be the one the oarsman can row on still water added by the flow of the river. In this case he can row the boat at speed of 3 mph, while the stream is 5 mph, so the speed from the observer standpoint is:

`speed = 3 + 5\\speed = 8 \text{ mph}`

The speed from the observer is 8 mph.