Useful skills: mathematics and physics

Basic mathematics and physics: So many things in nature seem to fit precise mathematical patterns. What we now call physics was once called natural philosophy. So rather than being alien and abstract, physics and mathematics are actually an attempt to understand natural phenomenon. You don’t have to be great at mathematics but you should have the fundamentals down. To be sure use paper only to see if you can do it without machines. practice occasionally. Make sure you can do long division on paper and get the right answer. Mathematics and physics still exist even if you don’t understand them, so you would be better served if you did understand. if you find the process hard write down all the information you have at the start attempting to give letters to each dimension and use the correct units. Meters, Kilograms, Litres, Volts, Amps, Ohms…write down all the relevant formulae  you know, and break the problem in to many small pieces.

I read a claim the other day stating the planet was hollow, base on the level of gravity we experience, it turns out the person did the calculation wrong:

g=GM/r²  (correct)  is not the same as g=  GM/r x r   =  GM (incorrect)

Math fail leading to massive misunderstanding of reality.

Not all of it is dry, abstract and boring, Fibonacci numbers and the golden ratio (1,1,2,3,5,8,13,21,34,55…) are widely seen in plants and animals if you know where to look.

Here is an example you should be able to do:

Balanced on a balance beam are 2 weights: on the left a 3 kg weight at 0.5 m form the center, and on the right another weight at 2 meters from the center what is its weight?

m1*d1 = m2*d2

Answer is 0.75 kg

Though you should be confident that you got to the right answer.


Get a second hand  high school final year physics book and read it slowly remembering there is no final exam and no pressure. Try to understand one new concept or formula per week . Look for real world examples to reinforce the newly gained knowledge.

If the maths is tripping you up get a mathematics book of a similar or lower level and try to see where you are going wrong. Remember science and maths are universal and work everywhere and the basics don’t change often or by very much. Apart from a bit of occasional practice you don’t really need to keep up with the latest developments.

Scram bag: Char cloth tin

Char cloth is one of the easier was to turn a spark into an ember, which of course can be turned into a flame.

To make the char cloth you will need a char cloth tin.

A great source of char cloth tins are empty nugget tins, though other well sealing tins can be used.

Kiwi boot polish tin.

Make char cloth tin:

1) Remove all paint from the tin with sand paper. (otherwise it will stink as it is heated)

2) Make a small vent hole 2-3 mm diameter (perhaps with a nail) in the top of the tin.

Use of char cloth tin:

1) Add small pieces of cut up natural cloth (20 mm square) into the tin and close it. (wood or paper can also be used)

2) Place tin on the embers of a fire with the vent  hole facing up.

3) Wait for smoke to come from the tin, and wait for the smoke to stop.

4) Turn the tin over so the vent hole faces down. ( this allows both sides of the cloth to char properly)

5)Wait for smoke to come from the tin, and wait for the smoke to stop.

6) Remove tin from the embers and allow to cool.

7) Open to inspect the char cloth.

Char cloth quality tests:

If  it is brown it need to be cooked longer.

If it is crumbly too the touch  it was cooked too long and must be discarded.

It should be black and soft but not too fragile.

Store the char cloth in an air tight container. A small piece of tape or bees wax over the vent hole may be enough.

Char cloth use:

Place char cloth in your fire starting kindling nest and place char cloth in the center.

Using what ever method you have of creating a spark, attempt to create sparks on the char cloth.

The cloth will smolder with red orange ember lines flowing through the material. blow on it gently in the kindling nest and flames should take hold.

Fun facts about kiwi boot polish:

Invented in Melbourne, Australia by Scottish immigrants, Made in Indonesia, and now owned in USA.

The US army just calls it Kiwi, just like they call the fruit a Kiwi.

Connection to new Zealand? One of the inventors wives was from New Zealand.

Allegedly this boot polish cemented the Kiwi as a symbol of New Zealand.

Cost: free* ( Some assembly required.) or possibly free with nugget for your boots.

Scram Bag: Sparking iron for fire lighting.

Not quite as primitive, difficult or slow as using friction on sticks.

Just get two lawn mower blade replacement tips heat them to red hot in a fire, if possible hammer them flat (the iron will be a lot softer when it is red hot), and allow to cool in the air.

The iron is now spark ready.

Welcome to the Iron age guys…

The blade tips don’t need to be new so they can be a re-use of a would be discarded item

Conveniently the pieces already have holes drilled in them so you can attach them together with a string/leather strip so you can keep them as a pair.

A with any other spark throwing device you will need to have a tinder birds nest ready to catch the spark.

This fire lighter will last a lifetime and if they get rusty you can just heat them again in the fire to remove the rust.

Alternate uses: could also be used as somewhat crude knives.

A large stack of lawnmower blade replacement tips. Made from carbon (mild or spring) steel.

Caution: If you are  working on or removing any part of a lawn mower blade, make sure the spark plug is disconnected and the blade cannot move.

Place large wooden objects into the path of the blades so in case they move you won’t loose a hand or finger(s). obviously its going to be hard to use a pair of sparking irons if you are missing hands or fingers.

Cost: free if you know where to look, other wise about $10 per pair.

Scram bag: Radio

Got to get information.

Access to information is very important and radio, while an old technology now, is likely to be one of the best sources of information during a crisis. AM radio is a particularly good source because of its range and likelihood of operation.

the DEGEN DE13 world receiver.

DEGEN DE13 Solar / windup/ 5V DC powered. Radio AM FM SW, LED flash light, red flashing LED, USB power output, and alarm.

This is a really great radio, packed with features.

A radio? You may think that because your mobile phone has a radio you’ve got it covered. Well partially. Mobile phones generally only receive FM radio and usually only with headphones attached as they double as the antenna.

FM is a relatively short range radio signal so if you are far from a transmitter you wont hear anything.

AM radio stations use large amounts of power and have large capacitors in order to operate, so that when the power goes off to radio stations FM stations only have generator reserves. AM stations will have a few days of electric reserves in their capacitors on top of generator reserves, so an AM receiver will be more likely to give you information and for longer. AM stations also have much longer range in reception as well.

Shortwave SW radio has enormous range, you’ll realize this when you start hearing languages other than English on them. Shortwave radio receivers are somewhat uncommon these day also.

Powering it.

Solar: A nice little polycrystalline panel.

Wind up: 60 turns of the handle for 1 hour of radio.

AAA cells: 3 AAA cells are an option.

micro USB port: the 5 pin connector, connect to a computer or other 5V DC source.

Lithium battery: Just like what is in cordless phones.


3 LED light, a pretty good light for shorter range illumination.

Red flashing LED, this is meant to be for reading maps at night, the red doesn’t affect you night vision too much.

Siren: I’m not sure how this is useful but its there.

USB output: I think this runs from the wind up only,  and has output limited to low current for charging older mobile phones or small electronic devices, but better than nothing (though the manual doesn’t specify).

Down sides.

Not waterproof, this can be mitigated buy using a small water proof container or bag.

Not dust proof, if your operating environment is very dusty of silty you could have trouble.

Antenna clasp is a bit fragile, fortunately this is not a critical component.

Battery case cover for the 3xAAA compartment seems a little flimsy.

No clock, one of the few products where the addition of a clock might have made sense, radio shows are scheduled to start at certain times, thought announcers do tend to quote the time often enough.

The instruction manual that comes with this device is pretty vaguely written, a bad translation from Chinese, it’s almost a throw away manual.

There is not form of charge indicator, just  charging LED (green) and a discharging LED (red).


Short wave radio stations sometimes talk about transmitting on X meters rather than a frequency.

This length distance they are talking about is the wave length of the radio wave, wavelength is usually given the Greek letter λ

c is the speed of light in a vacuum 299 792 458 m / s , you’ll notice this number is close to 300,000,000,  300 million or 3 x 10 ^8.

Frequency: f , measured in Hz (Hertz).

For example if someone was transmitting on 19 meters:

c  = λ  *  f

f =  c / λ

f = 300,000,000/19

f = 1,000,000   *  300/19

f = 1,000,000   *   15.79 Hz

f   = 15.79 MHz  (or 15,790 kHz )

This radio can detect that short wave frequency and those between 5.8 MHz and 18.2 MHz (51 to 16.5 meters in wavelength).

It should be noted that some SW bands are not in the frequency region where they should be due to some historical conventions.


Radio frequency notebook

You should create a series of notebook entries listing for each location you plan to be in which frequencies are operational and what type of information is given.


location 1

AM  frequency  information types

station 1             music and hourly news

station 2             news and weather (mostly prerecorded)

FM  frequency  information types

station 3        music  (infrequent news)

SW frequency  information types

station 4        Chinese language (shipping?)


A great deal of information can be inferred from which stations are still broadcasting also with what information they are giving.


This handy radio comes in several colors; dark green(pictured), lime green fluoro, and white, though I’m sure almost any color is possible

Can be bought from many internet sellers for about $30.

Scram bag: Vice grips

Vice grips as I have previously mentioned, are far superior to pliers.

6 pairs of vice grips. The two in the center are needle nose.

A remarkably versatile tool, they are simple to use and very durable.

They allow you to dial in a specific jaws distance( the screw knob on the end of the handle) and clamps onto an object.

I once pulled out a glued in wooden dowel out of a piece of kit-set furniture with vice grips, they are really strong.

They are extremely useful, allowing you to do things that require three hands and use only two.

Vice grips can also be used as a vice if attached to a stable platform.

Vice grips can also me use as a semi permanent clamp to hold things together.

Can also be used as a spanner or shifter, and if you are a bit desperate a hammer (nice flat sides).

They are so good I recommend you have 2 sets of vice grips, one large and one small.

Needle nose are very much worth considering as as models with cutters and the back of the jaws, other jaw arrangements tend to be a little to specialized for all round uses.

Some of the pliers based multi tool manufactures are catching on to the vice grips trend, but still a good pair of vice grips costs dramatically less.

Vice grips a really great versatile compact tool, let your mind run wild.

Every set of pliers one day hopes to grow up to be a set of vice grips.

Buyers guide, make sure the bottom jaw doesn’t slop too much (side to side and up and down) and that the screw adjustment is smooth and precise.

Usually made from chrome vanadium steel so they wont easily rust or corrode.

Cost $10-20 available at most hardware/ building supply stores.