How Can We Avoid That Hurricane?

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Math Level Required: Basic
Physics Level Required: Problems 1 and 2: Electromagnetic Waves
                                           Problem 3 and above: Coriolis Effect

Important Note: If you are unable to see the video clips that I've placed on this web page, it's probably because your browser is set to show only the "secure" content.  You will need to change your browser settings to have it display ALL content, both secure and non-secure.  If you don't know how to do that, come talk to me.

There's a lot of physics involved in this question.  First, we need to know where the hurricane is and what direction it's going.  Next, we need to know what direction to expect the winds to come from in order to move to the "safest" part of the storm, since we might not be able to move fast enough to get completely out of its way.

The first issue we have to deal with is that we're having trouble receiving the weather faxes we need in order to know where the hurricane is and which way it's moving.

Click on the triangle icon to see the video clip. 
(Be patient. If you have a slow internet connection it might take a while to download.)

Question 1: What is it that's interferring with our radio reception? 

Need help?  Think about the nature of radio waves.  What kind of waves are they?  Think about the clues given in the video clip.  What might be happening that could affect these types of waves with the kind of pattern that is described in the video clip?

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The trick described in that last video clip for getting better radiofax reception was nice and simple.  Too simple.  It doesn't always work, and so if that's the only trick you know for improving radio reception then you're in trouble.  In order to reliably receive the weather faxes we need a much better understanding of long-distance radio transmission and how to take advantage of atmospheric conditions that could either help or hinder radio reception.

Click on the triangle icon to see the video clip. 
(Be patient. If you have a slow internet connection it might take a while to download.)
 
Question 2: Write up a report as described in the preceding video clip telling why it is that sometimes one frequency works better for radio transmission but other times a different frequency works better.  The more in depth you go into describing how radio waves interact with the Earth's ionosphere the more points you'll get.  Be sure to explain what the different layers are in the Earth's ionosphere, why the strengths of those layers change according to the time of day and according to the strength of the solar wind, why it is that some radio frequencies interact with some layers in the ionosphere while other frequencies interact with other layers and why some frequencies don't interact with the ionosphere at all.  If all you do in your paper is just repeat the things that I said in the video clip then you won't get any points.

OK, so let's suppose that we find an adequate solution to the radio reception problem and therefore we know where the hurricane is and what direction it's moving.  What do we do if we can't move fast enough to get completely out of it's way?

A hurricane is a low-pressure storm system.  It draws air in from hundreds of miles around.  Because of a physics phenomenon called the "Coriolis effect" the wind directions near a hurricane always follow the same pattern.  If we know that pattern then we can (hopefully) position ourselves in a sector of the storm that's less dangerous than other sectors.

Question 3:  What is the "Coriolis effect" and why does it occur?

Need help?  Look on page 216 of the AMES Honors Physics textbook.  The General Physics Textbook doesn't cover this topic at all so if you're in that class then either borrow an Honors Physics Textbook or else try Googling it.  

Here's a YouTube video that does a pretty good job of explaining the Coriolis effect.  My only beef with the video is that they use the term "rotational velocity" incorrectly.  Hopefully those of you in the honors physics class or the U of U physics class will recognize that what the folks in the video call "rotational velocity" is actually "tangential linear velocity".  Despite what they say in the video, rotational velocity does not change as you move closer to the axis of rotation.  Remember that rotational velocity is measured in angular units per unit of time (like degrees per hour or like radians per second) .  The thing that does change as you move closer to the axis of rotation is tangential linear velocity, which is measured in linear units per unit of time (like miles per hour or meters per second).  But other than that minor wording goof, the rest of what they say in the video is very good and their demonstrations are excellent.

(If you're reading this on an AMES computer you won't be able to see this video because YouTube is blocked at school.  If that's the case then watch this from your home and it should work fine.)



Question 4:  Draw a picture of a hurricane as viewed from outer space and show what directions the winds will be blowing if the storm is located in the northern hemisphere.

Question 5:  Draw a picture of a hurricane as viewed from outer space and show what directions the winds will be blowing if the storm is located in the southern hemisphere.

Question 6:  On the picture that you've drawn for the hurricane in the northern hemisphere, draw an arrow showing that the storm is moving in a northwesterly direction.  Suppose you are in a boat that's located directly in the path of the oncoming storm and you can't move fast enough to out run it.  What direction should you go?... northeast or southwest?  If you answer this question correctly then your odds of surviving the storm will be considerably higher than they will be if you answer it wrong.  In order to get credit for this problem you need to explain WHY you chose the answer that you did.  Random guessing in this situation can be deadly.

Need help?  Consider the fact that a sailboat can handle strong winds and rough waves far better if it is "running" with the wind and waves coming from behind it.  If it tries to "beat into" the strong wind and the rough waves (where the wind and the waves are coming from ahead of the boat) then it won't go very well, if at all.  (A sail boat can beat into the wind if the wind isn't too strong and the waves aren't too big, but it can't do that in hurricane-force winds and waves.) 

Next, consider the fact that you definitely do NOT want to position the boat in a place where the prevailing wind direction is going to blow you towards the line that the center of the storm is moving along.  You want to position the boat so that when you run with the wind behind you, you'll be moving away from that line and thus away from the center of the storm.

Question 7:  On the picture that you've drawn for the hurricane in the southern hemisphere, draw an arrow showing that the storm is moving in a southwesterly direction.  Suppose you are in a boat that's located directly in the path of the oncoming storm and you can't move fast enough to out run it.  What direction should you go?... northwest or southeast?  As with the previous question, if you answer this question correctly then your odds of surviving the storm will be considerably higher than they will be if you answer it wrong.  Also as before, in order to get credit for this problem you need to explain WHY you chose the answer that you did.  

What if for some reason we aren't able to receive weather faxes?  
Suppose we know that a hurricane is approaching but we aren't sure whether we're directly in its path, to the right of its path, or to the left of its path.

Question 8:   What should we do?  As mentioned above, "beating" into the wind is a losing strategy in heavy weather.  We've got only two choices... we can steer so that we "run" downwind with the wind coming from the right rear side of the boat, or we can "run" downwind with the wind coming from the left rear side of the boat.  Which one is the safest strategy if you're in the northern hemisphere and why?  

Question 9:  Which option from the previous question is the safest strategy if you're in the southern hemisphere and why?


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