# Homework Help: Time needed to cross river - depends on flow of the water?

1. Sep 6, 2006

### parker21

When you swim across a river does the time to reach the opposite shore depend on the rate of flow of the water? Defend your answer

2. Sep 6, 2006

### Staff: Mentor

What do you think?

3. Sep 6, 2006

### Bystander

Couple hints: since it isn't stated in the problem, what do you want to assume about the width of the river; and, what do you want to assume for a relationship between the starting and ending points for your swim?

4. Sep 6, 2006

### rcgldr

The time is affected if the rate of flow has a component perpendicular to the path of the river, or if the river gets wider or narrower downstream, or if the rate of flow causes the water to get turbulent (probably other factors as well). You left out a lot of constraints in your original post.

5. Sep 7, 2006

### andrevdh

Will the speed of the water flow influence the speed of the swimmer (assuming that he always swim at the same speed) ?

6. Sep 14, 2006

### robi

yes, when you are travelling in the direction of flow your speed increases (as the speed of the flow is added to your own speed).similarily when you are going against the flow your speed reduces (as the speed of flow is restricting and is subtracted from your own speed).

7. Sep 14, 2006

### J77

...but that's not really across the river, is it?

Think about a flow down the river as you swim across it and, like said before, the width of the river and distance swam.

8. Sep 14, 2006

### Gokul43201

Staff Emeritus
Can we please require the OP present his/her thoughts before everyone else jumps in with their ideas?

9. Sep 14, 2006

### J77

Huh? http://img228.imageshack.us/img228/835/policexn6.gif [Broken]

It looked like the OP had drawn a conclusion - which didn't really go along with the question posed.

Last edited by a moderator: May 2, 2017
10. Sep 14, 2006

### Staff: Mentor

All the OP did was post the question!

As Gokul said, please resist the temptation to jump in prematurely.

11. Sep 14, 2006

### J77

Oops

I thought the robi person above me was the OP

Sorry!

And sorry Gokul - I thought you were enforcing the law