Swimming against the current

[GreyWanderer]

A friend told me it was better to swim towards the current at an angle instead of straight on. Is that true? In that case, why?

[DanishDynamite]

It would seem to depend on what you are trying to accomplish and where you are trying to go.

[zakur]

If you're talking about escaping from a swift-moving stream or river, you should never swim against the current — straight on or at an angle — because it will just tire you out. You should swim with the current and angle yourself toward the bank whenecer you can. Also, try to keep your body horizontal to the surface. This will minimize the chances of being pulled under.

[GreyWanderer]

You're trying to swim against the current.

Like if the current has driven you away from the shore, and you need to get back.

[Elaborate]

You mean like in a rip tide? If so, your friend is partially right. Because a rip tide is only 20 or 30 feet wide, you can get out of it before you are pulled too far from shore by swimming sideways. Once you are out, you can swimback to shore without having to fight the current.

[GreyWanderer]

Originally posted by Elaborate
You mean like in a rip tide? If so, your friend is partially right. Because a rip tide is only 20 or 30 feet wide, you can get out of it before you are pulled too far from shore by swimming sideways. Once you are out, you can swimback to shore without having to fight the current.

Let's just assume the current is the same everywhere. Wouldn't it be easier to just swim straight towards it?

I guess it would be like walking up a hill. You could walk either straight up or sideways. Sideways is easier, but it takes more time. Walking straight up will require the least energy, right?

[The Central Scrutinizer]

If you find yourself swimming against the tide and being pulled out to sea, it is best to give up and let yourself go. After you have drowned you will be in god's hands. Or the sharks will eat you. Whichever.

[LucyR]

Well, without thinking too much about it, I'd expect that you'd have to consider the effect of non-conservative forces. The water resistance as a function of your velocity (i.e. direction and magnitude) may imply that there is some minimum in the total energy expenditure.

Anyway, your post made me think of a puzzle you might like that's vaguely related:

An aircraft flies from point A to point B and back again. It now does the same, but this time a wind blows with a constant velocity from B to A. Question: is the round trip time the same, less than, or greater than in the first case? You have 10 seconds....

[Mahatma Kane Jeeves]

Elaborate is right. Here are some links. Plus, I saw them do a piece on this on Dateline.

http://www.ripcurrents.noaa.gov/

http://www.usatoday.com/weather/tg/wriptide/wriptide.htm

[LucyR]

Mahatma,

Yes, but in his last post he asked us to assume that the current is uniform.

[Mahatma Kane Jeeves]

:o

[LucyR]

...your links were still interesting, though. Thanks.

[fishbob]

People swim slow. Currents can be fast. Currents are often narrow. So - you can tire yourself out making no progress directly against a current or you can try to get out of the main current by swimming perpendicular to the current direction. Swimming upstream is for salmon.

[GreyWanderer]

Ok, thanks for the replies. I understand that my problem isn't realistic, but the answers I got will do. (:

[DrMatt]

In a related vein, weather folk say "don't try to outrun a tornado--run at right angles to its path."

[zakur]

And while we're at it — what's the deal with running from an alligator or crocodile? Some say zig-zag pattern, some say straight.

[Elaborate]

Up a tree would be my choice. While I've heard that alligators dan run faster than a man, I'm pretty sure they can't climb better than me.

[Skeptical Greg]

Originally posted by GreyWanderer
A friend told me it was better to swim towards the current at an angle instead of straight on. Is that true? In that case, why?

I don't know if this is true, but couldn't you actually move upstream (slowly) with little or no effort, much the same as sailing against the wind,(in a sail boat) by tacking?

[rwald]

I definitely heard running zig-zag from a croc. I think it had something to do with their only being able to run straight...

[bjornart]

Originally posted by Diogenes


I don't know if this is true, but couldn't you actually move upstream (slowly) with little or no effort, much the same as sailing against the wind,(in a sail boat) by tacking?

Um. No. When tacking, the wind gives you the energy to move forward. When you're swimming against the current you have to fight it, no matter what angle you swim at.

It only makes sense to swim at an angle to the current if you're:
[list=a]
Trying to fight a narrow current and can reach the edge of it.
Trying to cross a stream and don't want to end up far down the other bank.
[/list=a]

[BillyJoe]

Diogenes' answer (sail boat analogy) was probably what Grey Wanderer's friend was thinking of when he said it's better to swim at an angle to the current.

bjornart is correct that the sail boat analogy is incorrect. The swimmer is totally immersed in the current (of water) whereas the sailboat is only partially immersed in the current (of air). Its keel progects out of the air current and into the water which provides a counterforce to the air current.

Grey wanderer is correct in his initial post but for the wrong reason (the hill-climbing analogy). If you swim directly into the current, you expose a smaller surface area against which the current acts than if you swim at an angle to the current.

It's like skydiving: If you fall with your body horizontal your speed is less than if you fall with your body vertical (head first towards the ground)

[Always Free]

Well--don't go in the water in the first place especially if there are currents, rips, white water or crocs.

If on the beach, only swim where they are patrolled by life savers. If no life savers, don't go in. Simple. As for fast flowing rivers, nah, no way.

[BillyJoe]

It's your lucky day, AF, swim to your hearts content for I am a lifesaver and I will be there to revive you when you drown. :cool:

[MRC_Hans]

Well, I guess all has already been said, still:

The idea is that a person doesnt swim very fast (not even a good swimmer), so if you swim directly agains the current, chances are you are not getting anywhere, so you'll just tire out and drown. Swimming at (more or less) right angles to the current at least brings you somewhere, where the current might be less. Current is rarely strong over a really great area.

Now, if you are in the middle of the ocean (presumably you fell overboard or your boat sank), you wont be able to swim to your safety, so all you can do is preserve your energy by just staying afloat and hope somebody will come and save you.

Hans

[zakur]

Originally posted by rwald
I definitely heard running zig-zag from a croc. I think it had something to do with their only being able to run straight... Yeah, I had always heard that, but now I hear some experts saying just the opposite. Take for instance this page (http://www.flmnh.ufl.edu/cnhc/cbd-faq-q4.htm) from the Florida Museum of Natural History's Crocodilian Biology Database:MYTH! It is often said that you can outwit a crocodile by running in a zig-zag fashion away from it. This isn't true! Humans can out run crocodiles on land, and a straight line is the fastest way of putting distance between yourself and the crocodile. Most crocodile attack victims never see the crocodile coming - they use surprise, not speed.

[BillyJoe]

Originally posted by MRC_Hans
Well, I guess all has already been said, still..... ....which means, according to you, that all hasn't already been said.

Originally posted by MRC_Hans
.....The idea is that a person doesnt swim very fast (not even a good swimmer).... It's all relative, Hans, it's all relative!.......

Originally posted by MRC_Hans
.....so if you swim directly agains the current, chances are you are not getting anywhere, so you'll just tire out and drown. Depends on how fast the current is, how fast you can swim, how good your endurance is and how far you have to swim to get somewhere safe....

Originally posted by MRC_Hans
Swimming at.....right angles to the current at least brings you somewhere, where the current might be less.....but Grey Wonder asked you to consider the current to be the same everywhere :rolleyes:

Originally posted by MRC_Hans
Now, if you are in the middle of the ocean.....all you can do is preserve your energy by just staying afloat and hope somebody will come and save you. And now you're avoiding answering the question :mad:

[Always Free]

Originally posted by BillyJoe
It's your lucky day, AF, swim to your hearts content for I am a lifesaver and I will be there to revive you when you drown. :cool:

BJ, you're not pulling my leg are ya?

Hey, that's great, I know a life saver:D

Where do you 'save lives'? Which beach?

[BillyJoe]

Originally posted by Always Free
BJ, you're not pulling my leg are ya? Um.....er..........yes. :o

Originally posted by Always Free
Hey, that's great, I know a life saver:D Good for you, AF, good for you.....:(

Originally posted by Always Free
Where do you 'save lives'? Which beach? er.....why do you ask? :o


...scary...


BillyJoe

[Always Free]

*Bugger*!

[espritch]

From what I understand, crocodiles can indeed run faster than a man, but they can only keep it up for a very short time. If a crocodile misses it's initial strike, it is unlikely to chase you since it is more exposed out of water and would have a harder time draging you into the water if it did catch you (crododiles kill their prey by drowning them). Plus it would tire quickly.

I've also heard that you can escape a bear by running down a step slope because bears have difficulty running down hill due to the fact that their front legs are longer than their back legs. Anyone know if this is actually true?

[BillyJoe]

Originally posted by Always Free
*Bugger*! Nope. :)

[MRC_Hans]

Originally posted by BillyJoe
....which means, according to you, that all hasn't already been said.

No, it means that even if all had been said, I couldnt resist trying to look smart by summing it up in me own way ;)

It's all relative, Hans, it's all relative!.......

Realivity is handled in another thread ----

Depends on how fast the current is, how fast you can swim, how good your endurance is and how far you have to swim to get somewhere safe....

If you can't swim faster than the current, you aint gonna get nowhere, unless safety is downstream, in which case you oughtta swim that way :rolleyes:

....but Grey Wonder asked you to consider the current to be the same everywhere :rolleyes:

If the current is the same everywhere, you are in the middle of the ocean, so it doesn't really matter which way you swim :D

And now you're avoiding answering the question :mad:

No, just answering another one :p

Hans

[LucyR]

BillyJoe,

Why the unprovoked attack on Hans? He's not a bad chap for an engineer.

[MRC_Hans]

'tis my own fault, I'm sure. Comes from being around Franko too much. The troll scent rubs off.

Anyhoo, I dont mind trolling from time to time ;) A little trolling is like spice.

Hans

[BillyJoe]

.....and I suppose I could have added a few more smilies :( :D :cool: ;)

[fishbob]

I've also heard that you can escape a bear by running down a step slope because bears have difficulty running down hill due to the fact that their front legs are longer than their back legs. Anyone know if this is actually true? I wouldn't count on it. Bears can run faster than humans over long distances and they can run much faster than humans for short bursts. I read an article years ago about running speed of bipedal critters vs quadrapeds. I recall that 4 legs are more efficient at converting energy into speed.

[Skeptical Greg]

Originally posted by fishbob
I wouldn't count on it. Bears can run faster than humans over long distances and they can run much faster than humans for short bursts. I read an article years ago about running speed of bipedal critters vs quadrapeds. I recall that 4 legs are more efficient at converting energy into speed.

Oh No!! Just thought of " running faster than bear " joke..


Two guys in forest are discussing what to do if they see a bear..

1st guy: All I have to do is take off running..

2nd guy: You can't outrun a bear..

1st guy: I can outrun you though....:D

[BillyJoe]

Hey?....Oh yeah , I get it.....the second guy's a cannibal.....good one Diogenes :D

:cool: