# Fisherman saling up stream and drops cork travels back .

• teddyayalew
In summary, the fisherman's speed relative to the water is equal to the current's speed, which is 5km/hour. This was determined by setting the time the fisherman rowed upstream and downstream equal to each other and using the fact that the boathook traveled 5km in the same amount of time.
teddyayalew

## Homework Statement

A fisherman is sailing up-stream; when passing under a bridge, he drops a boat-hook in the water. After half an hour he discovers this, turns back, and overtakes the boat-hook 5km below the bridge. What is the speed of the current if the fisherman rows at the same speed up and down the river?

x=vt

## The Attempt at a Solution

I have drawn the diagram to visualize what is going on
http://i40.tinypic.com/2qvtdop.jpg

and defined certain equations
http://i42.tinypic.com/34ir8fq.jpg

I understand that the hook traveled 5km downward along along the stream after
30min +xmins but I am having trouble figure out how to solve for x so that I may solve for the velocity of the stream

teddyayalew said:

## Homework Statement

A fisherman is sailing up-stream; when passing under a bridge, he drops a boat-hook in the water. After half an hour he discovers this, turns back, and overtakes the boat-hook 5km below the bridge. What is the speed of the current if the fisherman rows at the same speed up and down the river?

x=vt

## The Attempt at a Solution

I have drawn the diagram to visualize what is going on
http://i40.tinypic.com/2qvtdop.jpg

and defined certain equations
http://i42.tinypic.com/34ir8fq.jpg

It would be easier on your readers if you included your equations in the body of the post.
You should also write down all equations.

I understand that the hook traveled 5km downward along along the stream after
30min +xmins but I am having trouble figure out how to solve for x so that I may solve for the velocity of the stream

The first step in solving any problem is to write down the equations, and to do this you will have to define some variables. So, let $v_{r}$ be the speed the fisherman rows at wrt the water, and let $v_{c}$ be the speed of the current. Let $t_u$ be the time the fisherman rowed upstream, let $t_d$ be the time the fisherman rowed downstream, and let simple $t$ be the total time. Let $x_h$ be the distance the boathook floated downstream. You may need some more variables.

Now let upstream be the positive $x$ direction, and let the bridge be $x = 0$.

Now write down equations for the fisherman's trip and for the boathook's trip. From those you should be able to see how to solve the problem.

Last edited:
Thank you so much I was able to arrive at the right solution. I found that
TIME(u) = TIME(d) so then V(c) * (TIME(u) + TIME(d)) = V(c) * one hour

and we know the cork traveled 5km during the total time so
V(c) *one hour = 5km ,,, V(c) = 5km/hour!

## 1. Why does the fisherman sail up stream?

The fisherman sails up stream because he is most likely trying to reach a specific spot where he can catch fish or to follow the path of the fish as they swim upstream.

## 2. How does the cork travel back when the fisherman drops it?

The cork travels back due to the current of the stream. The force of the water pushes the cork back towards the fisherman.

## 3. Is it common for fishermen to sail up stream?

Yes, it is common for fishermen to sail up stream, especially when they are targeting fish that swim upstream during certain seasons.

## 4. What is the purpose of dropping the cork while sailing up stream?

Dropping the cork while sailing up stream helps the fisherman gauge the strength and direction of the current. It also helps them locate potential fishing spots.

## 5. Does the direction of the current affect the cork's travel back to the fisherman?

Yes, the direction of the current plays a significant role in the cork's travel back to the fisherman. If the current is strong, the cork will travel back quickly, and if the current is weak, the cork may not travel back at all.